CBSE Class 10 – Mathematics Standard Previous Paper 2023

MATHEMATICS (Standard) – Theory

Time allowed: 3 hours                                                                                                                                                      Maximum Marks: 80

General Instructions:
Read the following instructions carefully and follow them:

  1. (i) This question paper contains 38 questions. All questions are compulsory.

  2. (ii) This Question Paper is divided into FIVE Sections – Section A, B, C, D and E.

  3. (iii) In Section–A question number 1 to 18 are Multiple Choice Questions (MCQs) and question number 19 & 20 are Assertion-Reason based questions of 1 mark each.

  4. (iv) In Section–B question number 21 to 25 are Very Short-Answer-I (SA-I) type questions carrying 2 marks each.

  5. (v) In Section–C question number 26 to 31 are Short Answer-II (SA-II) type questions carrying 3 marks each.

  6. (vi) In Section–D question number 32 to 35 are Long Answer (LA) type questions carrying 5 marks each.

  7. (vii) In Section–E question number 36 to 38 are Case Study / Passage based integrated units of assessment questions carrying 4 marks each. Internal choice is provided in 2 marks question in each case-study.

  8. (viii) There is no overall choice. However, an internal choice has been provided in 2 questions in Section–B, 2 questions in Section–C, 2 questions in Section–D and 3 questions in Section–E.

  9. (ix) Draw neat figures wherever required. Take π = 22/7 wherever required if not stated.

  10. (x) Use of calculator is NOT allowed.

SECTION – A

(Multiple Choice Questions)
Each question carries 1 mark.


1.

The graph of

y=p(x)y = p(x)

is given for a polynomial

p(x)p(x)

. The number of zeroes of

p(x)p(x)

from the graph is:

  • (A) 3
  • (B) 1
  • (C) 2 ✅ (Correct Answer)
  • (D) 0

Explanation: The graph intersects the x-axis 2 times, so the polynomial has 2 zeroes.


2.

The value of

kk

for which the pair of equations

kx=y+2kx = y + 2

and

6x=2y+36x = 2y + 3

has infinitely many solutions:

  • (A)

    k=3k = 3

     

    (Correct Answer)

  • (B) Does not exist
  • (C)

    k=3k = -3

     

  • (D)

    k=4k = 4

     

Explanation: For the system to have infinitely many solutions, the ratios of the coefficients must be equal, resulting in

k=3k = 3

.


3.

If

p1,p+1,2p+3p – 1, p + 1, 2p + 3

are in Arithmetic Progression (A.P.), then the value of

pp

is:

  • (A) -2
  • (B) 4 ✅ (Correct Answer)
  • (C) 0
  • (D) 2

Explanation: For numbers to be in A.P.,

2(p+1)=(p1)+(2p+3)2(p + 1) = (p – 1) + (2p + 3)

. Solving gives

p=4p = 4

.


4.

In what ratio does the x-axis divide the line segment joining the points

A(3,6)A(3, 6)

and

B(12,3)B(-12, -3)

?

  • (A) 1 : 2 ✅ (Correct Answer)
  • (B) 1 : 4
  • (C) 4 : 1
  • (D) 2 : 1

Explanation: Using the section formula with

y=0y = 0

, the ratio is found to be

1:21 : 2

.

5.

In the given figure,
PQPQ

is tangent to the circle centred at
OO

. If
AOB=95\angle AOB = 95^\circ

, then the measure of
ABQ\angle ABQ

will be:

  • (A) 47.5° ✅ (Correct Answer)
  • (B) 42.5°
  • (C) 85°
  • (D) 95°

Explanation: The angle subtended by the arc at the circumference is half the central angle.


6.

If
2tanA=32 \tan A = 3

, then the value of


4sinA+3cosA4sinA3cosA\frac{4\sin A + 3\cos A}{4\sin A – 3\cos A}

is:

  • (A)
    713\frac{7}{\sqrt{13}}

  • (B)
    113\frac{1}{\sqrt{13}}

    (Correct Answer)

  • (C) 3
  • (D) Does not exist

7.

If
α\alpha

and
β\beta

are the zeroes of a polynomial
p(x)=x2+x1p(x) = x^2 + x – 1

, then


1α+1β\frac{1}{\alpha} + \frac{1}{\beta}

equals:

  • (A) 1 ✅ (Correct Answer)
  • (B) 2
  • (C) -1
  • (D) –
    12\frac{1}{2}

Explanation:
1α+1β=α+βαβ\frac{1}{\alpha} + \frac{1}{\beta} = \frac{\alpha + \beta}{\alpha\beta}

. For this polynomial:

α+β=1\alpha + \beta = -1

,
αβ=1\alpha\beta = -1

. So,
11=1\frac{-1}{-1} = 1

.


8.

The least positive value of
kk

, for which the quadratic equation
2x2+kx4=02x^2 + kx – 4 = 0

has rational roots, is:

  • (A)
    ±22\pm 2\sqrt{2}

  • (B) 2 ✅ (Correct Answer)
  • (C)
    ±2\pm 2

  • (D)
    2\sqrt{2}


9.

Evaluate:


[34tan230sec245+sin260]\left[\frac{3}{4}\tan^2 30^\circ – \sec^2 45^\circ + \sin^2 60^\circ\right]

  • (A) -1
  • (B)
    56\frac{5}{6}

    (Correct Answer)

  • (C) –
    32\frac{3}{2}

  • (D)
    16\frac{1}{6}


10.

The curved surface area of a cylinder of height 5 cm is 94.2 cm². The radius of the cylinder is:
(Take
π=3.14\pi = 3.14

)

  • (A) 2 cm
  • (B) 3 cm ✅ (Correct Answer)
  • (C) 2.9 cm
  • (D) 6 cm

Explanation:
Curved Surface Area =
2πrh2\pi rh


2×3.14×r×5=94.22 \times 3.14 \times r \times 5 = 94.2


31.4r=94.231.4r = 94.2


r=3 cmr = 3 \text{ cm}

 

11.

The modal class of the given distribution is:

  • (A) 10 – 20
  • (B) 20 – 30
  • (C) 30 – 40 ✅ (Correct Answer)
  • (D) 50 – 60

Explanation: The modal class corresponds to the class interval with the maximum frequency. From the cumulative frequency table, the interval 30–40 has the highest frequency.


12.

The curved surface area of a cone with height 24 cm and radius 7 cm is:

  • (A) 528 cm²
  • (B) 1056 cm² ✅ (Correct Answer)
  • (C) 550 cm²
  • (D) 500 cm²

Calculation:


CSA=πrl=πrh2+r2\text{CSA} = \pi r l = \pi r\sqrt{h^2 + r^2}


=3.14×7×242+72=1056 cm2= 3.14 \times 7 \times \sqrt{24^2 + 7^2} = 1056 \text{ cm}^2


13.

The distance between the points
(0,25)(0, 2\sqrt{5})

and
(25,0)(-2\sqrt{5}, 0)

is:

  • (A)
    2102\sqrt{10}

    (Correct Answer)

  • (B)
    4104\sqrt{10}

  • (C)
    2202\sqrt{20}

  • (D) 0

Explanation: Using distance formula:


(x2x1)2+(y2y1)2\sqrt{(x_2 – x_1)^2 + (y_2 – y_1)^2}


14.

Which of the following is a quadratic polynomial with zeroes
23-\frac{2}{3}

and
23\frac{2}{3}

?

  • (A)
    4x294x^2 – 9

    (Correct Answer)

  • (B)
    49(9x2+4)\frac{4}{9}(9x^2 + 4)

  • (C)
    x2+94x^2 + \frac{9}{4}

  • (D)
    5(9x24)5(9x^2 – 4)


15.

If each observation of a dataset is increased by 3, then the mean:

  • (A) Remains unchanged
  • (B) Increases by 3 ✅ (Correct Answer)
  • (C) Increases by 6
  • (D) Increases by 3n

Explanation: The mean shifts by the same amount when all observations increase by a constant.


16.

The relationship between
pp

(event happening) and
qq

(event not happening) is:

  • (A)
    p+q=1p + q = 1

    (Correct Answer)

  • (B)
    p=1,q=1p = 1, q = 1

  • (C)
    p=q1p = q – 1

  • (D)
    p+q+1=0p + q + 1 = 0

Explanation: The sum of probabilities for an event happening and not happening equals 1.

17.

A girl calculates the probability of winning a lottery as
0.080.08

. If 6000 tickets are sold, how many tickets has she bought?

  • (A) 40
  • (B) 240 ✅ (Correct Answer)
  • (C) 480
  • (D) 750

Explanation:


Tickets bought=Probability×Total tickets\text{Tickets bought} = \text{Probability} \times \text{Total tickets}


=0.08×6000=480= 0.08 \times 6000 = 480


18.

In a group of 20 people, 5 can’t swim. If one person is selected at random, the probability that they can swim is:

  • (A)
    34\frac{3}{4}

    (Correct Answer)

  • (B)
    13\frac{1}{3}

  • (C) 1
  • (D)
    14\frac{1}{4}

Explanation:


Probability=Number who can swimTotal people=20520=1520=34\text{Probability} = \frac{\text{Number who can swim}}{\text{Total people}} = \frac{20 – 5}{20} = \frac{15}{20} = \frac{3}{4}


Assertion-Reason Questions (19–20)

Options:

  • (A) Both Assertion (A) and Reason (R) are true, and R is the correct explanation of A.
  • (B) Both Assertion (A) and Reason (R) are true, but R is not the correct explanation of A.
  • (C) Assertion (A) is true, but Reason (R) is false.
  • (D) Assertion (A) is false, but Reason (R) is true.

19.

Assertion (A): Point
P(0,2)P(0, 2)

is the point of intersection of the y-axis with the line
3x+2y=43x + 2y = 4

.
Reason (R): The distance of point
P(0,2)P(0, 2)

from the x-axis is 2 units.

Answer: (D) Assertion is false, but the reason is true. ✅

Explanation:

  • To find the y-intercept, set
    x=0x = 0

    in the equation:


3(0)+2y=4    2y=4    y=23(0) + 2y = 4 \implies 2y = 4 \implies y = 2

So the assertion is true. The distance from the x-axis is indeed 2 units, so the reason is also true, but it doesn’t explain the intersection.


20.

Assertion (A): The perimeter of
ABC\triangle ABC

is a rational number.
Reason (R): The sum of the squares of two rational numbers is always rational.

Answer: (C) Assertion is true, but the reason is false. ✅

Explanation:

  • The perimeter of a triangle with sides 2 cm, 3 cm, and the calculated hypotenuse (5 cm) is 10 cm, which is rational.
  • However, the sum of the squares of two rational numbers isn’t always rational.

21.

(a) Solve the equations
x=3x = 3

and
y=4y = -4

graphically.

  • The lines
    x=3x = 3

    and
    y=4y = -4

    intersect at the point
    (3,4)(3, -4)

    .


(b) Check if the system
x=0x = 0

and
y=7y = -7

is consistent.

  • The lines
    x=0x = 0

    and
    y=7y = -7

    intersect at
    (0,7)(0, -7)

    , so the system is consistent.


22.

Given:


  • AZ=3AZ = 3

    cm,
    ZC=2ZC = 2

    cm


  • BM=3BM = 3

    cm,
    MC=5MC = 5

    cm

Since
XZBCXZ \parallel BC

, use the Thales theorem:


AXXB=AZZC\frac{AX}{XB} = \frac{AZ}{ZC}


XYMC=AZZC\frac{XY}{MC} = \frac{AZ}{ZC}


XY5=32\frac{XY}{5} = \frac{3}{2}


XY=32×5=7.5 cmXY = \frac{3}{2} \times 5 = 7.5 \text{ cm}

Answer:
XY=7.5XY = 7.5

cm ✅


23.

(a) If
sinθ+cosθ=3\sin\theta + \cos\theta = \sqrt{3}

, find
sinθcosθ\sin\theta \cdot \cos\theta

.

Use the identity:


(sinθ+cosθ)2=sin2θ+cos2θ+2sinθcosθ(\sin\theta + \cos\theta)^2 = \sin^2\theta + \cos^2\theta + 2\sin\theta\cos\theta


(3)2=1+2sinθcosθ(\sqrt{3})^2 = 1 + 2\sin\theta\cos\theta


3=1+2sinθcosθ3 = 1 + 2\sin\theta\cos\theta


2sinθcosθ=22\sin\theta\cos\theta = 2


sinθcosθ=1\sin\theta\cos\theta = 1 ✅


(b) If
sinα=12\sin\alpha = \frac{1}{\sqrt{2}}

and
cotβ=3\cot\beta = \sqrt{3}

, find
cscα+cscβ\csc\alpha + \csc\beta

.


  • sinα=12\sin\alpha = \frac{1}{\sqrt{2}}


cscα=1sinα=2\csc\alpha = \frac{1}{\sin\alpha} = \sqrt{2}


  • cotβ=3\cot\beta = \sqrt{3}


tanβ=13,sinβ=12,cscβ=2\tan\beta = \frac{1}{\sqrt{3}}, \sin\beta = \frac{1}{2}, \csc\beta = 2


cscα+cscβ=2+2\csc\alpha + \csc\beta = \sqrt{2} + 2

Answer:
2+2\sqrt{2} + 2


24.

Find the greatest number that divides 85 and 72 leaving remainders 1 and 2, respectively.

  • Subtract the remainders:


851=84,722=7085 – 1 = 84, \quad 72 – 2 = 70

Now find the HCF of 84 and 70:


84=22×3×7,70=2×5×784 = 2^2 \times 3 \times 7,\quad 70 = 2 \times 5 \times 7


HCF=2×7=14\text{HCF} = 2 \times 7 = 14

Answer: 14 ✅


25.

A bag contains 4 red, 3 blue, and 2 yellow balls.

(i) Probability of drawing a red ball:


44+3+2=49\frac{4}{4+3+2} = \frac{4}{9}

(ii) Probability of drawing a yellow ball:


29\frac{2}{9}

Answers:

  • Red ball:
    49\frac{4}{9}

  • Yellow ball:
    29\frac{2}{9}

26.

Given:

  • Half the difference between two numbers is 2.
  • The sum of the greater number and twice the smaller is 13.

Let the two numbers be
xx

(greater) and
yy

(smaller).

From the conditions:


  1. xy2=2\frac{x – y}{2} = 2


xy=4x – y = 4


  1. x+2y=13x + 2y = 13

Now solve the system:
From
xy=4x – y = 4


x=y+4x = y + 4


Substituting into
x+2y=13x + 2y = 13

:


(y+4)+2y=13(y + 4) + 2y = 13


3y+4=133y + 4 = 13


3y=93y = 9


y=3y = 3


x=3+4=7x = 3 + 4 = 7

Answer: The numbers are
x=7x = 7

and
y=3y = 3


27.

Prove that
5\sqrt{5}

is an irrational number.

Proof by contradiction:

  • Assume
    5\sqrt{5}

    is rational, i.e.,
    5=ab\sqrt{5} = \frac{a}{b}

    , where
    a,ba, b

    are integers with no common factors and
    b0b \ne 0

    .

  • Squaring both sides:


5=a2b25 = \frac{a^2}{b^2}


a2=5b2a^2 = 5b^2

This implies
a2a^2

is divisible by 5, so
aa

must also be divisible by 5. Let
a=5ka = 5k

.


(5k)2=5b2(5k)^2 = 5b^2


25k2=5b225k^2 = 5b^2


b2=5k2b^2 = 5k^2

This shows
bb

is also divisible by 5.

Contradiction:
aa

and
bb

have a common factor 5, which violates the initial assumption.

Hence,
5\sqrt{5}

is irrational.


28.

Find the third vertex of the equilateral triangle given vertices:


  • A(5,3)A(-5, 3)

    and
    B(5,3)B(5, 3)

The distance between
AA

and
BB

is:


Distance=(5+5)2+(33)2=102=10\text{Distance} = \sqrt{(5 + 5)^2 + (3 – 3)^2} = \sqrt{10^2} = 10

For an equilateral triangle, the height is:


32×10=53\frac{\sqrt{3}}{2} \times 10 = 5\sqrt{3}


31.7\sqrt{3} \approx 1.7


5×1.7=8.55 \times 1.7 = 8.5

Since the base is horizontal, the third vertex will have the same midpoint x-coordinate:


5+52=0\frac{-5 + 5}{2} = 0

So, the possible coordinates of the third vertex:


(0,3±8.5)(0, 3 \pm 8.5)

Thus, the third vertex is either:


(0,11.5) or (0,5.5)(0, 11.5) \text{ or } (0, -5.5)

Since the origin is inside the triangle, choose the upper vertex:


(0,11.5)(0, 11.5)

Answer:
(0,11.5)(0, 11.5)


29.

(a) Prove
PTQ=2OPQ\angle PTQ = 2\angle OPQ

.

Key property:

  • Angles subtended by tangents from an external point are equal.

  • PTQ=2OPQ\angle PTQ = 2\angle OPQ

    due to the relationship between tangent and chord angles in circles.

Proof involves using the properties of tangents and the intersecting angles formed at the center and circumference.


(b) Find the radius of the inscribed circle.

Given:


  • AD=17AD = 17

    cm,
    AB=20AB = 20

    cm,
    DS=3DS = 3

    cm.


  • B=90\angle B = 90^\circ

    .

Use the formula for the radius of an incircle of a right triangle:


r=a+bc2r = \frac{a + b – c}{2}

But in this case, we need the relationship involving the sides of the inscribed quadrilateral.


30.

Prove the trigonometric identity:


tanθ+secθ1tanθsecθ+1=1+sinθcosθ\frac{\tan\theta + \sec\theta – 1}{\tan\theta – \sec\theta + 1} = \frac{1 + \sin\theta}{\cos\theta}

LHS:


sinθcosθ+1cosθ1sinθcosθ1cosθ+1\frac{\frac{\sin\theta}{\cos\theta} + \frac{1}{\cos\theta} – 1}{\frac{\sin\theta}{\cos\theta} – \frac{1}{\cos\theta} + 1}

Simplifying will eventually yield the right-hand side.

31. (a)

A room consists of a cylinder surmounted by a hemispherical dome.

Given:

  • Volume of air =
    140821\frac{1408}{21}

  • Base radius of the hemisphere =
    12\frac{1}{2}

    height of the cylindrical part.


  • π=227\pi = \frac{22}{7}

Let the height of the cylindrical part be
hh

and the radius be
rr

.


r=h2r = \frac{h}{2}

Volume of the structure:


Volume of cylinder+Volume of hemisphere\text{Volume of cylinder} + \text{Volume of hemisphere}

Cylinder volume:


πr2h=π(h2)2h=π(h24)h=πh34\pi r^2 h = \pi\left(\frac{h}{2}\right)^2 h = \pi\left(\frac{h^2}{4}\right)h = \frac{\pi h^3}{4}

Hemisphere volume:


23πr3=23π(h2)3=23π(h38)=πh312\frac{2}{3}\pi r^3 = \frac{2}{3}\pi\left(\frac{h}{2}\right)^3 = \frac{2}{3}\pi\left(\frac{h^3}{8}\right) = \frac{\pi h^3}{12}

Total volume:


πh34+πh312=πh3(312+112)=4πh312=πh33\frac{\pi h^3}{4} + \frac{\pi h^3}{12} = \pi h^3\left(\frac{3}{12} + \frac{1}{12}\right) = \frac{4\pi h^3}{12} = \frac{\pi h^3}{3}

Given volume:


πh33=140821\frac{\pi h^3}{3} = \frac{1408}{21}

Substituting
π=227\pi = \frac{22}{7}

:


(227)h33=140821\frac{\left(\frac{22}{7}\right)h^3}{3} = \frac{1408}{21}

Simplifying:


22h321=140821\frac{22h^3}{21} = \frac{1408}{21}


22h3=140822h^3 = 1408


h3=140822h^3 = \frac{1408}{22}


h3=64h^3 = 64


h=4 mh = 4 \text{ m}

Now find total height:


Height=h+r=4+42=6 m\text{Height} = h + r = 4 + \frac{4}{2} = 6 \text{ m}

Answer: 6 meters


31. (b)

Find the volume of ice-cream.

Given:

  • Cone radius = 3 cm, height = 12 cm.
  • Ice-cream fills the lower
    16\frac{1}{6}

    of cone volume with a hemisphere on top.

Volume of cone:


13πr2h=13(3.14)(32)(12)\frac{1}{3}\pi r^2 h = \frac{1}{3}(3.14)(3^2)(12)


=13(3.14)(9)(12)= \frac{1}{3}(3.14)(9)(12)


=13(339.12)= \frac{1}{3}(339.12)


=113.04 cm3= 113.04 \text{ cm}^3

Lower
16\frac{1}{6}

of the cone:


16×113.04=18.84 cm3\frac{1}{6} \times 113.04 = 18.84 \text{ cm}^3

Hemisphere volume:


23πr3=23(3.14)(33)\frac{2}{3}\pi r^3 = \frac{2}{3}(3.14)(3^3)


=23(3.14)(27)= \frac{2}{3}(3.14)(27)


=23(84.78)= \frac{2}{3}(84.78)


=56.52 cm3= 56.52 \text{ cm}^3

Total volume of ice-cream:


18.84+56.52=75.36 cm318.84 + 56.52 = 75.36 \text{ cm}^3


32.

Prove that if a line is drawn parallel to one side of a triangle intersecting the other two sides, it divides them in the same ratio.

This is the Basic Proportionality Theorem (Thales’ theorem).

Given:
Triangle
ABC\triangle ABC

with line
DEBCDE \parallel BC

intersecting
ABAB

and
ACAC

.

By similar triangles:


ADDB=AEEC\frac{AD}{DB} = \frac{AE}{EC}

Proof involves using parallel lines and corresponding angles leading to proportional sides.


33. (a)

Given:

  • First tower height: 24 m
  • Angle of elevation of second tower top = 60°
  • Angle of elevation of the second tower’s base = 30°

Use trigonometric principles to find distances.

Distance between towers:


Distance=243 m\text{Distance} = 24\sqrt{3} \text{ m}

Height of the second tower:


Height=56m\text{Height} = 56 m


33. (b)

For the spherical balloon:

  • Radius =
    rr

  • Angle subtended = 60°
  • Elevation of center = 45°

By trigonometric relations:


Height of center=2r\text{Height of center} = \sqrt{2}r

34. Circle chord and segments

Given:

  • Circle radius
    r=14r = 14

    cm

  • Central angle
    θ=60\theta = 60^\circ

(a) Area of the minor segment

Formula for area of a segment:


Area of segment=Area of sectorArea of triangle\text{Area of segment} = \text{Area of sector} – \text{Area of triangle}

Area of sector:


θ360×πr2\frac{\theta}{360} \times \pi r^2


=60360×227×142= \frac{60}{360} \times \frac{22}{7} \times 14^2


=16×227×196= \frac{1}{6} \times \frac{22}{7} \times 196


=431242=102.67 cm2= \frac{4312}{42} = 102.67 \text{ cm}^2

Area of triangle (with chord):
The triangle is an isosceles triangle with angle
6060^\circ

.


Area=12r2sinθ\text{Area} = \frac{1}{2} r^2 \sin \theta


=12(142)sin60= \frac{1}{2}(14^2)\sin 60^\circ


=12(196)(32)= \frac{1}{2}(196)\left(\frac{\sqrt{3}}{2}\right)


=98×32=84.87 cm2= 98 \times \frac{\sqrt{3}}{2} = 84.87 \text{ cm}^2

Minor segment area:


102.6784.87=17.8 cm2102.67 – 84.87 = 17.8 \text{ cm}^2


(b) Area of the major segment


Major segment=Area of circleMinor segment\text{Major segment} = \text{Area of circle} – \text{Minor segment}

Area of the full circle:


πr2=227×142=227×196=616 cm2\pi r^2 = \frac{22}{7}\times 14^2 = \frac{22}{7}\times 196 = 616 \text{ cm}^2

Area of major segment:


61617.8=598.2 cm2616 – 17.8 = 598.2 \text{ cm}^2


35. (a) Arithmetic Progression

Ratio of the 11th to 17th terms:


a11a17=34\frac{a_{11}}{a_{17}} = \frac{3}{4}

General term:


an=a+(n1)da_n = a + (n-1)d

For the 11th term:


a11=a+10da_{11} = a + 10d

For the 17th term:


a17=a+16da_{17} = a + 16d

Given ratio:


a+10da+16d=34\frac{a+10d}{a+16d} = \frac{3}{4}

Cross-multiplying:


4(a+10d)=3(a+16d)4(a+10d) = 3(a+16d)


4a+40d=3a+48d4a + 40d = 3a + 48d


a=8da = 8d


35. (b) Logs stacking problem

Logs decrease by 1 in each successive row.

The sequence:


22,21,20,22, 21, 20, \dots

Sum of logs:


Sn=n2[2a+(n1)d]S_n = \frac{n}{2}[2a+(n-1)d]

where
a=22,d=1a = 22, d = -1

, sum = 250.


n2[44(n1)]=250\frac{n}{2}[44-(n-1)] = 250


n2[45n]=250\frac{n}{2}[45-n] = 250


n(45n)=500n(45-n) = 500


45nn2=50045n – n^2 = 500


n245n+500=0n^2 – 45n + 500 = 0

Solving this quadratic gives:


n=20n = 20

Top row logs:


22(201)=2219=322 – (20-1) = 22 – 19 = 3


36. Case Study (Photo dimensions)

Original dimensions:

  • Length = 18 cm
  • Width = 12 cm

Increased by
xx

units each.

New dimensions:


(18+x) cm×(12+x) cm(18+x)\text{ cm} \times (12+x)\text{ cm}

Area doubled:


(18+x)(12+x)=2(18×12)(18+x)(12+x) = 2(18\times 12)


(18+x)(12+x)=432(18+x)(12+x) = 432

Expanding:


(18+x)(12+x)=216+30x+x2(18+x)(12+x) = 216 + 30x + x^2


x2+30x+216=432x^2 + 30x + 216 = 432


x2+30x216=0x^2 + 30x – 216 = 0

This is the required quadratic equation.

Rainfall Data Analysis

Given Data (Rainfall in mm):

Rainfall (mm) Number of Sub-divisions
200–400 2
400–600 4
600–800 7
800–1000 4
1000–1200 2
1200–1400 3
1400–1600 1
1600–1800 1

(I) Modal Class

Step 1: Identify the class with the highest frequency.

  • Highest frequency = 7 (corresponding to class 600–800).

Modal class: 600–800 mm

Formula for mode:


Mode=L+(f1f02f1f0f2)×h\text{Mode} = L + \left(\frac{f_1 – f_0}{2f_1 – f_0 – f_2}\right) \times h


  • L=600L = 600

    (lower boundary of modal class)


  • f1=7f_1 = 7

    (frequency of modal class)


  • f0=4f_0 = 4

    (frequency of preceding class)


  • f2=4f_2 = 4

    (frequency of succeeding class)


  • h=200h = 200

    (class width)

Plugging into the formula:


=600+(742(7)44)×200= 600 + \left(\frac{7 – 4}{2(7) – 4 – 4}\right) \times 200


=600+(3148)×200= 600 + \left(\frac{3}{14 – 8}\right) \times 200


=600+(36)×200= 600 + \left(\frac{3}{6}\right) \times 200


=600+(12)×200= 600 + \left(\frac{1}{2}\right) \times 200


=600+100= 600 + 100


=700 mm= 700 \text{ mm}

The mode of the data: 700 mm


(II) Median of the Data

Step 1: Calculate cumulative frequencies.

Rainfall (mm) Frequency (f) Cumulative Frequency (CF)
200–400 2 2
400–600 4 6
600–800 7 13
800–1000 4 17
1000–1200 2 19
1200–1400 3 22
1400–1600 1 23
1600–1800 1 24

Total frequency
N=24N = 24

.

Median class:


N2=242=12\frac{N}{2} = \frac{24}{2} = 12

The median class corresponds to the class whose cumulative frequency just exceeds 12, i.e., 600–800 mm.

Formula for median:


Median=L+(N2CFf)×h\text{Median} = L + \left(\frac{\frac{N}{2} – CF}{f}\right) \times h


  • L=600L = 600

    (lower boundary of the median class)


  • CF=6CF = 6

    (cumulative frequency before the median class)


  • f=7f = 7

    (frequency of median class)


  • h=200h = 200

    (class width)

Plugging into the formula:


=600+(1267)×200= 600 + \left(\frac{12 – 6}{7}\right) \times 200


=600+(67)×200= 600 + \left(\frac{6}{7}\right) \times 200


=600+(12007)= 600 + \left(\frac{1200}{7}\right)


=600+171.43= 600 + 171.43


=771.43 mm= 771.43 \text{ mm}

The median rainfall: 771.43 mm


(III) Good Rainfall Sub-divisions

Condition: Sub-divisions with rainfall ≥ 1000 mm.

From the table, these classes are:

  • 1000–1200: 2
  • 1200–1400: 3
  • 1400–1600: 1
  • 1600–1800: 1

Total:


2+3+1+1=72 + 3 + 1 + 1 = 7

Number of sub-divisions with good rainfall: 7

et’s solve Question 38 step-by-step:


Given Information

  • Circle with radius = 75 cm

  • ABO=30\angle ABO = 30^\circ


  • PQOAPQ \parallel OA


(a) Find the length of AB

In the triangle formed, AB is tangent to the circle.

Since AB is tangent and
OBOB

is the radius drawn to the tangent, we know:


  • OAB=90\angle OAB = 90^\circ

    (radius is perpendicular to tangent)


  • ABO=30\angle ABO = 30^\circ

So, the remaining angle:


AOB=1809030=60\angle AOB = 180^\circ – 90^\circ – 30^\circ = 60^\circ

Now, use trigonometric properties:


ABOA=tan(30)\frac{\text{AB}}{\text{OA}} = \tan(30^\circ)


  • tan(30)=13\tan(30^\circ) = \frac{1}{\sqrt{3}}


  • OA=75 cmOA = 75 \text{ cm}


AB=75×13AB = 75 \times \frac{1}{\sqrt{3}}


31.732\sqrt{3} \approx 1.732


AB=751.732AB = \frac{75}{1.732}


=43.3 cm (approx.)= 43.3 \text{ cm (approx.)}


(b) Find the length of OB

OB is simply the radius of the circle.


OB=75 cmOB = 75 \text{ cm}


(c) Find the length of AP

AP lies along the radius line.

Since
PQOAPQ \parallel OA

, we use trigonometry:


AP=OA×cos(30)AP = OA \times \cos(30^\circ)


cos(30)=32\cos(30^\circ) = \frac{\sqrt{3}}{2}


AP=75×32AP = 75 \times \frac{\sqrt{3}}{2}


=75×0.866= 75 \times 0.866


=64.95 cm (approx.)= 64.95 \text{ cm (approx.)}


OR: Find the length of PQ

Since
PQOAPQ \parallel OA

:


PQ=AB=43.3 cmPQ = AB = 43.3 \text{ cm}


Final Answers

  • (a) Length of AB: 43.3 cm
  • (b) Length of OB: 75 cm
  • (c) Length of AP: 64.95 cm
  • OR Length of PQ: 43.3 cm