Book Name | : | Target Book |
Paper Type | : | School Test Question Paper (2024 – 2025) |
Paper Category | : | Madhyamik Suggestion |
School | : | The Scottish Church Collegiate School |
Table of Contents
ToggleQuestion – 1
Choose the correct answer for each of the following questions: [1 × 5 = 5]
(i) A principal amounts to 27/8 times in 3 years using compound interest. The rate of interest per annum is—
(a) 20%
(b) 50%
(c) 30%
(d) None of these.
Answer
(b) 50%
Explanation:
27\over 8P = P(1 + r\over 100)³
or, (3\over 2)³ = (1 + r\over 100)³
or, r\over 100 = 3\over 2 – 1
or, r\over 100 = 1\over 2
or, r = 1\over 2 × 100 % = 50%
(ii) If 5 + 2√6 = (√3 - √2)x , then the value of x is—
(a) 2
(b) -2
(c) 3
(d) -3
Answer
(b) -2
(iii) If a2bc and b2ca, then—
(a) c ∝ a
(b) c = constant
(c) abc = constant
(d) ab ∝ c
Answer
(c) abc = constant
(iii) In the right-angled triangle ABC, the lengths of the sides AB, BC, AC are 3 cm, 5 cm, and 4 cm. Radius of the incircle is—
(a) 1 cm
(b) 7 cm
(c) 2 cm
(d) 1.25 cm
Answer
(b) 7 cm
(iv) If sec α = cosec β, then the value of sin (α + β) is—
(a) 1/2
(b) 1/√2
(c) √3/2
(d) 1
Answer
(d) 1
Explanation:
1\over \text{cos α} = 1\over \text{sin β}
or, cos α = sin β
or, cos α = cos (90º – β)
or, α = 90º – β
or, α + β = 90º
sin (α + β) = sin 90º = 1
(v) y = 2x – 5 and the median of x is 16. The median of y is—
(a) 25
(b) 27
(c) 32
(d) 28
Answer
(b) 27
Explanation:
y = 2x – 5
or, y = 2(16) – 5 = 27
Question – 2
Fill in the blanks (Any Five): [1 × 5 = 5]
(i) The interest of Re. 1 in 1 month at 1% rate of simple interest per annum is ____.
(ii) If one root of the equation x² – 6x + k = 0 is twice the other, then the value of k is ____.
(iii) If y = z – 1/x, z = x – 1 and x – y = 1/z, then the sum of the constant of variation is ____.
(iv) ABCD is a cyclic trapezium, AB is the diameter of the circle and AB || CD. If ∠BCD = 110°, then the value of ∠BDC is ____.
(v) The ratio of the volume of a sphere and a cube circumscribing the sphere is ____.
(vi) If x cos θ = 1 and tan θ = y, then the value of x² – y² is ____.
(vii) If the mean of x1, x2, x3, …, xn is x̄, then the mean of ax1, ax2, ax3, …, axn is ____.
Answer
(i) ₹0.01
(ii) 8
(iii) 3
(iv) 70°
(v) π/6
(vi) 1
(vii) ax̄
Question – 3
State whether True or False (Any Five): [1 × 5 = 5]
(i) At the same rate of interest, the simple interest for 2 years is more than the compound interest on the same principal.
(ii) Number of real roots of the equation (x – 1)² + (x – 2)² + (x – 3)² = 0 is three.
(iii) The circumference of a right-angled triangle is at the midpoint of the hypotenuse.
(iv) The value of sin θ is always greater than 1.
(v) If tan(θ + 15°) = 1, then cos 2θ = 1/2.
(vi) In a frequency distribution, table median is the term with the highest frequency.
Answer
(i) False; At the same rate of interest, the compound interest for 2 years is more than the simple interest on the same principal due to interest being calculated on the accumulated amount.
(ii) False; The number of real roots of the equation (x – 1)² + (x – 2)² + (x – 3)² = 0 is zero because the sum of squared terms cannot be zero unless all terms are zero, which is not possible here.
(iii) True
(iv) False; The value of sinθ lies between −1 and 1, so it can never be greater than 1 1.
(v) True
(vi) False; In a frequency distribution, the mode is the term with the highest frequency, not the median.
Question – 4
Answer the following Questions (Any Ten): [2 × 10 =20]
(i) In a joint business, the ratio of capitals of A, B, C are 1\over4 : 1\over3 : 1\over8 . At the end of the year, B’s share of profit is ₹500 more than C’s share of profit. Find the total profit in the business.
Answer
Ratio of capitals of A, B and C = 1\over4 : 1\over3 : 1\over 8 = 6 : 8 : 3
Profit of A = 6x
Profit of B = 8x
Profit of C = 3x
ATP:
Profit of B – Profit of C = 500
or, 8x – 3x = 500
or, 5x = 500
or, x = 100
Total profit = 6x + 8x + 3x = 17x
= 17 × 100 = ₹ 1700
(ii) A sum of money becomes twice in n years at r% compound rate of interest per annum. In how many years will it be 4 times?
Answer
Let principal (P) = x
Amount (A) = 2x
2x = x(1+r)n
or, 2 = (1+r)n
Squaring Both Side
or, 4 = (1+r)2n
It will take 2n years for the sum of money to become 4 times.
(iii) If (5 + 2√6)x – (5 – 2√6)x = 98, then find the value of x.
Answer
x = ± 2
For x = 2
(5 + 2√6)2 + (5 – 2√6)2
= 25 + 20√6 + 24 + 25 – 20√6 + 24
= 98
(iv) If the roots of the equation (1 + m²)x² + 2mcx + (c² – p²) = 0 are real and equal, then prove that c² = p²(1 + m²).
Answer
(1 + m²)x² + 2mcx + (c² – p²) = 0.
For real and equal roots, the discriminant Δ must be zero.
Discriminant formula:
Δ = b² – 4ac,
where a = 1 + m², b = 2mc, and c = c² – p².
Substitute:
Δ = (2mc)² – 4(1 + m²)(c² – p²).
Δ = 4m²c² – 4[(1 + m²)(c² – p²)].
Δ = 4[m²c² – c² + p² + m²p²].
Set Δ = 0:
m²c² – c² + p² + m²p² = 0.
c² = p² + m²p².
c² = p²(1 + m²).
Thus, c² = p²(1 + m²).
(v) If 1\over x + 1\over y ∝ 1\over x + y, then show that x ∝ y.
(vi) Evaluate: sin6α + cos6α + 3sin²αcos²α.
Answer
(sin2α)3 + (cos2α)3 + 3 sin²α cos²α
= (sin2α + cos2α)(sin4α -sin²α cos²α + cos4α) + 3 sin²α cos²α
= (sin2α)2 – sin²α cos²α + (cos2α) + 3 sin²α cos²α
= (sin2α)2 + (cos2α)2 + 2 sin²α cos²α
= (sin2α + cos2α)2 – 2 sin²α cos²α + 2 sin²α cos²α
= 1 + 0 = 1
(vii) In ΔABC, AB = (2a – 1) cm, AC = 2√2a cm, and BC = (2a + 1) cm, then find the value of ∠BAC.
(viii) Find the height, slant height, and diameter of a right circular cone are h, l, d, then find the value of (l² – h²)/d².
Answer
Using l2 = h2 + r2
or, l2 – h2 = (d/2)2
or, \text{l}² - \text{h}² = \text{d}² \over 4
or, \text{l}² - \text{h}² \over \text{d}² = 1 \over 4
(ix) Find the ratio of the volume of a sphere and the cylinder circumscribing the sphere.
Answer
Volume of a sphere = 4\over3πr3
Volume of Cylinder = πr2h = 2πr3
Ratio = Volume of a sphere : Volume of Cylinder
= 4\over3πr3 : 2πr3
= 2\over3 = 2 : 3
The ratio of the volume of the sphere to the volume of the cylinder is 2:3.
(x) What is the measure of each side of the cube formed by melting three cubes of sides 3 cm, 4 cm, and 5 cm?
Answer
Volume of cube side 3 cm = 33 = 27 cm3
Volume of cube side 4 cm = 43 = 64 cm3
Volume of cube side 5 cm = 53 = 125 cm3
Total volume = 27 cm3 + 64 cm3 + 125 cm3 = 216 cm3
Side of cube = \sqrt[3]{216} = 6 cm
(xi) If r cos θ = 2√3 and rsinθ = 2, 0 < θ < 90°, find the value of r and θ.
Answer
r cos θ = 2√3
or, (r cos θ)2 = (2√3)2
or, r2 cos2 θ = 12 — (a)
r sin θ = 2
or, r2 sin2 θ = 22
or, r2 sin2 θ = 4 — (b)
Now adding (a) and (b)
r2 sin2 θ + r2 cos2 θ = 4 + 12
or, r2 (sin2 θ + cos2 θ) = 16
or, r2 = 16
or, r = 4
Now, r sin θ = 2
sin θ = 2/4 = 1/2
or, sin θ = sin 30º
or, θ = 30º
∴ θ = 30º and r = 4
(xii) The average of a frequency distribution is 24, Σfx = 1700 + 35p and Σf = 80 + p. Find the value of p.
Answer
Mean = Σfx / Σf.
Given:
Mean = 24, Σfx = 1700 + 35p, and Σf = 80 + p.
24 = (1700 + 35p) / (80 + p)
or, 24(80 + p) = 1700 + 35p
or, 1920 + 24p = 1700 + 35p
or, 1920 – 1700 = 35p – 24p
or, 220 = 11p
or, p = 220 / 11 = 20
Question – 5
Answer any One of the following Questions: [5 × 1 = 5]
(i) Due to a campaign against tobacco each year, the number of smokers reduces by 6 1\over4 %. In a city at present, the number of smokers is 33,750. What was the number of smokers three years ago?
Answer
Present Population (V) = ₹ 33,750
rate (r) = 25\over4%
time (n) = 3 years
Initial Population (Vo) = ?
Present Population (V) = Vo(1 – 25\over4×100)3
or, 33750 = Vo (1 – 1\over 16)3
or, 33750 = Vo (15\over 16)3
or, Vo = 33750 × 16 × 16 × 16\over 15 × 15 × 15 = 40,960.
The number of smokers three years ago was approximately 40,960.
(ii) A and B started a business investing ₹60,000 and ₹75,000 respectively. After 4 months, C joined the business investing ₹40,500, then A and B withdrew that money according to their capital. At the end of the year, if total profit is ₹19,575, then find their share of profit.
Answer
Investment of A = ₹ 60,000 × 12 = ₹ 7,20,000
Investment of B = ₹ 75,000 × 12 = ₹ 9,00,000
Investment of C = ₹ 40,500 × 8 = ₹ 3,24,000
Ratio of capital = 7,20,000 : 9,00,000 : 3,24,000
= 40 : 50 : 18
Sum of ratio = 40 + 50 + 18 = 108
A’s profit share = 40\over 108× 40 = ₹7,250.
B’s profit share = 40\over 108 × 50 = ₹9,062.50.
C’s profit share = 40\over 108 × 18 = ₹3,262.50.
Question – 6
Answer any One Question: [3 × 1 = 3]
(i) Solve: x+3\over x-3 + x-3\over x+3 = 21\over 2
Answer
x+3\over x-3 + x-3\over x+3 = 5\over 2
or, (x+3)² + (x-3)²\over (x-3)(x + 3) = 5\over 2
or, x² + 6x + 9 + x² - 6x + 9\over x² - 9 = 5\over 2
or, 2x² + 9\over x² - 9 = 5\over 2
or, 4x2 + 36 = 5x2 − 45.
or, -x2 = – 45 – 36
or, – x2 = – 81
or, x2 = 81
or, x = ± 9
(ii) If α and β are the roots of the equation ax² + bx + c = 0, then find the value of 1\over \text{(bα + c)} + 1\over \text{(bβ + c)}.
Answer
Sun of roots (α + β) = – \text {b} \over \text {a}
Product of roots (α × β) = \text {c} \over \text {a}
Now, 1\over \text{(bα + c)} + 1\over \text{(bβ + c)}
= \text{(bβ+c)+(bα+c)} \over \text{(bα+c)(bβ+c)}
= \text{b(α+β)+2c.} \over \text{b²αβ+bc(α+β)+c²}
= \text{- b(b/a)+2c.} \over \text{b²(c/a)-bc(b/a)+c²}
= \text{−b²+2ac}\over \text{ac²}
Question – 7
Answer any One Question: [3 × 1 = 3]
If x = √3/2, then find the value of √(1 + x) + √(1 – x).
Answer
beyond syllabus
If x, y, z are variables such that y + z + x = constant and (x – y + z)(x + y – z) ∝ xyz, then prove that (y + z – x) α xyz.
Answer
beyond syllabus
Question – 8
(i) If \text{a}\over \text{b+c} + \text{b}\over \text{c+a} + \text{c}\over \text{a+b} = 1, then show that \text{a}²\over \text{b+c} + \text{b}²\over \text{c+a} + \text{c}²\over \text{a+b} = 0
Answer
beyond syllabus
(ii) If \text{b}\over \text{a+b} = \text{a+c-b}\over \text{b+c-a}=\text{a+b+c}\over \text{2a+b+2c} when a + b + c ≠ 0, then show that a/2 = b/3 = c/4
Answer
beyond syllabus
Question – 9
Answer any One Question: [5 × 1 = 5]
(i) State and prove Pythagoras’ theorem.
Answer
Pythagoras Theorem: In any right-angled triangle, the area of the square drawn on the hypotenuse is equal to the sum of the areas of the squares drawn on the other two sides.
Given: ABC is a right-angled triangle whose ∠A is a right angle.
To prove: BC² = AB² + AC²
Construction: I draw a perpendicular AD on the hypotenuse BC from the right angular point A which intersects the side BC at the point D.
Proof: In right-angled Δ ABC, AD is perpendicular on the hypotenuse BC.
∴ Δ ABD and Δ CBA are similar.
Hence,
{\text{AB} \over \text{BC}} = {\text{BD} \over \text{AB}},
∴ AB² = BC × BD —- (i)
Again, ΔCAD and ΔCBA are similar.
Hence,
{\text{AC} \over \text{BC}} = {\text{DC} \over \text{AC}}
∴ AC² = BC × DC —- (ii)
So, by adding (i) and (ii), I get:
AB² + AC² = BC × BD + BC × DC.
= BC (BD + DC) = BC × BC = BC².
∴ BC² = AB² + AC² [proved]
(ii) Prove that on the same arc of a circle, the angle at the center is twice the angle at the circumference.
Answer
Given: ∠AOB is the angle at the center of the circle with center O, and ∠ACB is the angle at any point on the circle formed by the circular arc APB.
To Prove: ∠AOB = 2∠ACB
Construction: C, O are joined, and CO is extended up to the point D.
Proof:
In △AOC,
OA = OC in each case (radii of the same circle).
∴ ∠OCA = ∠OAC (∠s opp to equal side are equal)
Again, Side CO of Δ AOC is extended up to point D.
Exterior ∠AOD = ∠OAC + ∠OCA = 2∠OCA — (I)
In ΔBOC
OB = OC in each case (radii of the same circle).
Again, since side CO of ΔBOC is extended up to point D:
∴ Exterior ∠BOD = ∠OCB + ∠OBC = 2 ∠OCB — (II)
∠AOD + ∠BOD = 2∠OCA + 2∠OCB
∴ ∠AOB = 2(∠OCA + ∠OCB) = 2∠ACB — (III)
∴ ∠AOB = 2∠ACB (Proved)
Question – 10
Answer any One Question:
(i) In ΔABC, Δ is a right angle. If AD ⊥ BC, then prove that \text{ΔABC}\over \text{ΔACD} = \text{BC²}\over \text{AC²}.
Answer
Given:
In right angled ΔABC, A = 90º and AD is perpendicular on hypotenuse BC.
To Prove: \text{ΔABC}\over \text{ΔACD} = \text{BC²}\over \text{AC²}
Proof: Δ ACD ∼ Δ ABC
\text{AC}\over \text{BC} = \text{AD}\over \text{AB} = \text{CD}\over \text{AC}
or, \text{AC}\over \text{BC} = \text{CD}\over \text{AC}
∴ AC² = BC. CD
Now, \text{ΔABC}\over \text{ΔACD} = ½ \text{BC × AD}\over ½ \text{CD × AD} = \text{BC}\over \text{CD}
= \text{BC²}\over \text{CD.BC}
= \text{BC²}\over \text{CD.BC}
Substitute AC² = BC. CD
= \text{BC²}\over \text{AC<sup>²</sup>}
(ii) ABCD is a cyclic quadrilateral. AB and DC are extended to meet at P. Prove that PA·PB = PC·PD.
Answer
Given: In cyclic quadrilateral ABCD, the extended two sides of AB and DC meet at the point P.
To prove: PA · PB = PC · PD
Proof:
ABCD is a cyclic quadrilateral.
∴ ∠DAB + ∠DCB = 180°
Again, ∠DCB + ∠BCP = 180°
∴ ∠DAB + ∠DCB = ∠DCB + ∠BCP
∴ ∠DAB = ∠BCP … (i)
In ΔAPD and ΔCPB, ∠APD = ∠CPB [Same angle]
and ∠DAP = ∠BCP [from (i)]
∴ ΔAPD and ΔCPB are similar.
∴ PA / PC = PD / PB
∴ PA · PB = PC · PD (Proved)
Question – 11
Answer any One Question:
(i) In a triangle, one side of length is 6.8 cm having two adjacent angles 60° and 75°. Draw the triangle and also draw the incircle of the triangle.
Answer
(ii) Construct a square whose area is equal to the area of a triangle of sides 8 cm, 7 cm, and 5 cm.
Answer
Not in syllabus
Question – 12
Answer any Two Questions:
(i) If α + β = π/2, then show that (sec α + sin β)/sin α = tan α + 2 tan β.
Answer
LHS : \text{1/cos α + sin β}\over \text{sin α}
= {\text{1 + sin β cos α} \over \text{cos α}} \over \text{sin α}
= \text{1 + cos α × sin β} \over \text{sin α cos α}
= 1\over \text{sin α cos α} + \text{cos α × cos α} \over \text{sin α cos α}
= 1\over \text{sin α cos α} + \text{cos α × cos α} \over \text{sin α cos α}
= \text{sin² α + cos² α}\over \text{sin α cos α} + cot α
= \text{sin² α} \over \text{sin α cos α} + \text{cos² α} \over \text{sin α cos α} + cot α
= tan α + cot α + cot α
= tan α + 2 cot α
= tan α + 2 cot β = RHS (Proved)
(ii) Show that (tan α + sec α – 1)/(tan α – sec α + 1) = (1 + sin α)/cos α.
Answer
LHS: \text{tan α + sec α - 1}\over \text{tan α - sec α + 1}
= \text{tan α + sec α - (sec² α - tan² α)}\over \text{tan α - sec α + 1}
= \text{(sec α + tan α) - (sec α + tan α)(sec α - tan α)}\over \text{tan α - sec α + 1}
= \text{(sec α + tan α)[1 - (sec α - tan α)]}\over \text{tan α - sec α + 1}
= \text{(sec α + tan α)(tan α - sec α + 1)}\over \text{tan α - sec α + 1}
= sec α + tan α
= \text{1}\over \text{cos α} + \text{sin α}\over \text{cos α}
= \text{1 + sin α}\over \text{cos α} = RHS (Proved)
(iii) If 81sin²θ + 81cos²θ = 30, find the value of θ.
Answer
81sin²θ + 81cos²θ = 30
or, 81sin²θ + 811 – sin²θ = 30
or, 81sin²θ +81\over 81^ {sin²θ} = 30
Let 81sin²θ = x, we get
x + 81\over x = 30
or, x2 + 81 = 30x
or, x2 – 30x + 81 = 0
or, (x – 27)(x – 3) = 0
∴ x = 27 or 3
For x = 27 | For x = 3 |
81sin²θ = 27 or, 34sin²θ = 33 When bases are same power are equal 4sin²θ = 3 or, sin²θ = 3\over 4 or, sin θ = √3\over 2 or, sin θ = sin 60º or, θ = 60º | 814sin²θ = 3 or, 34sin²θ = 31 When bases are same power are equal 4sin²θ = 1 or, sin²θ = 1\over 4 or, sin θ = 1\over 2 or, sin θ = sin 30º or, θ = 30º |
∴ θ = 30º and 60º
Question – 13
Answer any one Questions:
(i) The angle of elevation of a cloud from a point h meter above a lake is α, and the angle of depression of its reflection in the lake is β. Prove that the height of the cloud is h(tan β + tan α)/(tan β – tan α).
Answer
(ii) A round balloon of radius r subtends an angle θ at the eye of the observer while the angle of elevation of its center is ϕ. Prove that the height of the center of the balloon is r sin ϕ cosec (θ/2).
Answer
Question – 14
(i) A water tank of length 21 dcm, breadth 11 dcm, and depth 6 dcm is half full of water. If 100 iron spheres of diameter 21 cm are immersed, then what length in dcm the water level will rise?
Answer
The tank has dimensions:
- Length = 21 decimeters,
- Breadth = 11 decimeters,
- Depth = 6 decimeters.
Volume = Length×Breadth×Depth.
= 21 × 11 × 6 = 1386 dcm³.
Initial water volume = 1\over2 × 1386 = 693dcm³.
The diameter of each iron sphere is 21 cm = 2.1 dcm
radius = 1.05 dcm
Volume of a sphere = 4\over3πr3
= 4\over3π(1.05)3 cm³
Total volume of 100 spheres = 4\over3π(1.05)3 × 100 cm³
Base area of the tank = Length × Breadth × h
= 21 × 11 × h = 231h dcm³ .
ATP: 231h = 4\over3π(1.05)3
or, h = 4\over3π(1.05)3 ÷ 231 = 2.1 decimeters
(ii) The height of a cylinder is twice its radius of base. When the height is 6 times the base, the volume increased by 539 cubic cm. What is the height of the cylinder?
Answer
Initial height = 2r
Final height = 6r
The difference in volumes = 539 cubic cm.
πr²(6r) – πr²(2r) = 539
or, 6πr³ – 2πr³ = 539
or, 4πr³ = 539
or, 4 × 22\over 7r³ = 539
or, r³ = 539 × 7\over 22 × 4 = 42.875
or, r = 3.5 cm
or, h = 6r = 6 × 3.5 = 21 cm
The height of the cylinder is 21 cm.
(iii) The sides of a right-angled triangle are 3 cm, 4 cm, and 5 cm. The triangle is rotated about the hypotenuse, then two right circular cones are formed. Find the total volume of the cone to make this formed.
Answer
Cone 1: Base radius = 3 cm, Height = 4 cm.
Volume = 1\over3πr2h
= 1\over3 × π × 32 × 4 = 12π cm³
Cone 2: Base radius = 4 cm, Height = 3 cm.
Volume = 1\over3πr2h
= 1\over3 × π × 42 × 3 = 16π cm³
The total volume of the two cones = 12π cm³ + 16π cm³
= 28π cm³
Question – 15
(i) From the data given below, draw an ogive and find the median of the following distribution:
Class Interval | Frequency |
---|---|
50-55 | 2 |
55-60 | 8 |
60-65 | 12 |
65-70 | 12 |
70-75 | 24 |
75-80 | 16 |
80-85 | 4 |
Answer
Class Interval | Cummulative Freq |
---|---|
Less than 50 | 0 |
Less than 55 | 2 |
Less than 60 | 10 |
Less than 65 | 22 |
Less than 70 | 34 |
Less than 75 | 58 |
Less than 80 | 74 |
Less than 85 | 78 |
(ii) The median of the given table is 32. If the sum of the frequencies is 100, find x and y.
Class Interval | Frequency |
---|---|
0-10 | 14 |
10-20 | 27 |
20-30 | x |
30-40 | 25 |
40-50 | y |
50-60 | 10 |
Answer
Class Interval | Frequency | Cummulative Freq |
---|---|---|
0-10 | 14 | 14 |
10-20 | 27 | 41 |
20-30 | x | 41 + x |
30-40 | 25 | 66 + x |
40-50 | y | 66 + x + y |
50-60 | 10 | 76 + x + y |
Median Class = 30-40
Median = L + {N\over 2 - CF}\over f × h
or, 32 = 30 + {100\over 2 - (41 + x)}\over 25 × 10
or, {50 - (41 + x)}\over 25 × 10 = 32 – 30
or, {9 - x}\over 25 × 10 = 2
or, (9 – x) × 10 = 2 × 25
or, (9 – x) × 10 = 2 × 25
or, 9 – x = 5
or, x = 4
Now, 76 + x + y = 100
or, 76 + 4 + y = 100
or, y = 100 – 80 = 20
∴ x = 4 and y = 20
(iii) If the mode of the distribution is 24, find the value of x.
Class Interval | Frequency |
---|---|
0-10 | 14 |
10-20 | 27 |
20-30 | 21 |
30-40 | x |
40-50 | 5 |
Answer
Mode = L + f_m - f_{m-1}\over 2f_m - f_{m-1} - f_{m+1} × h
The mode is given as 24, which lies in the class 20-30. Thus:
- L = 20,
- fm = 21,
- fm-1 = 27,
- fm+1 = x,
- h = 10.
or, 24 = 20 + 21 - 27\over 2 × 21 - 27 - x × 10
or, 24 = 20 + -6\over 15 - x × 10
or, 24 = 20 – 60\over 15 - x
or, 24 – 20 = – 60\over 15 - x
or, 4 = – 60\over 15 - x
or, 4(15 – x) = -60.
or, 60 – 4x = -60.
or, 4x = 120.
or, x = 30.
∴ Final Answer: x = 30