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NDA / CDS / AFCAT

NDA, CDS, AFCAT — Maths, GK, English

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Difficulty: All Easy Medium Hard 31–40 of 47
Topics in NDA / CDS / AFCAT
All Mathematics (NDA) 100
Q.31 Medium Mathematics (NDA)
What is the compound interest on Rs. 8000 at 10% per annum for 2 years?
A Rs. 1680
B Rs. 1600
C Rs. 1800
D Rs. 1500
Correct Answer:  A. Rs. 1680
EXPLANATION

A = P(1 + r/100)ⁿ = 8000(1.1)² = 8000 × 1.21 = 9680. CI = 9680 - 8000 = 1680.

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Q.32 Medium Mathematics (NDA)
If ABCD is a rhombus with diagonals 6 cm and 8 cm, find its area.
A 24 cm²
B 48 cm²
C 28 cm²
D 56 cm²
Correct Answer:  A. 24 cm²
EXPLANATION

Area of rhombus = (1/2) × d₁ × d₂ = (1/2) × 6 × 8 = 24 cm².

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Q.33 Medium Mathematics (NDA)
If log₁₀ 2 = 0.301, find log₁₀ 200.
A 2.301
B 2.602
C 1.301
D 3.301
Correct Answer:  A. 2.301
EXPLANATION

log₁₀ 200 = log₁₀(2 × 100) = log₁₀ 2 + log₁₀ 100 = 0.301 + 2 = 2.301.

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Q.34 Medium Mathematics (NDA)
The average of five numbers is 35. If one number is replaced by 50, the new average becomes 38. What was the original number?
A 30
B 35
C 40
D 45
Correct Answer:  B. 35
EXPLANATION

Sum of 5 numbers = 35 × 5 = 175. New sum = 38 × 5 = 190. Difference = 190 - 175 = 15. Original number = 50 - 15 = 35.

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Q.35 Medium Mathematics (NDA)
If cos θ = 7/25 and θ is acute, find tan θ.
A 7/24
B 24/7
C 25/24
D 24/25
Correct Answer:  B. 24/7
EXPLANATION

cos θ = 7/25 means adjacent = 7, hypotenuse = 25. Using Pythagoras, opposite = 24. tan θ = opposite/adjacent = 24/7.

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Q.36 Medium Mathematics (NDA)
In a triangle, if one angle is 90° and the other two angles are in ratio 1:2, the angles are:
A 30°, 60°, 90°
B 45°, 45°, 90°
C 20°, 70°, 90°
D 40°, 50°, 90°
Correct Answer:  A. 30°, 60°, 90°
EXPLANATION

One angle = 90°. Other two in ratio 1:2. Let them be x and 2x. x + 2x + 90 = 180 → 3x = 90 → x = 30°. Angles are 30°, 60°, 90°.

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Q.37 Medium Mathematics (NDA)
The volume of a cone with radius 5 cm and height 12 cm is: (use π = 22/7)
A 314.29 cm³
B 628.57 cm³
C 471.43 cm³
D 314.86 cm³
Correct Answer:  A. 314.29 cm³
EXPLANATION

Volume of cone = (1/3)πr²h = (1/3) × (22/7) × 25 × 12 = (1/3) × (22/7) × 300 = 314.29 cm³.

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Q.38 Medium Mathematics (NDA)
If a quadratic equation has roots α and β, and α + β = 7, αβ = 10, what is the equation?
A x² - 7x + 10 = 0
B x² + 7x + 10 = 0
C x² - 7x - 10 = 0
D x² + 7x - 10 = 0
Correct Answer:  A. x² - 7x + 10 = 0
EXPLANATION

Quadratic equation is x² - (sum of roots)x + (product of roots) = 0, which gives x² - 7x + 10 = 0.

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Q.39 Medium Mathematics (NDA)
If the ratio of two numbers is 3:5 and their sum is 64, find the larger number.
A 24
B 32
C 40
D 48
Correct Answer:  C. 40
EXPLANATION

Let numbers be 3x and 5x. 3x + 5x = 64 → 8x = 64 → x = 8. Larger number = 5 × 8 = 40.

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Q.40 Medium Mathematics (NDA)
Find the value of (x³ - 8)/(x - 2) when x ≠ 2.
A x² + 2x + 4
B x² - 2x + 4
C x² + 2x - 4
D x² - 2x - 4
Correct Answer:  A. x² + 2x + 4
EXPLANATION

x³ - 8 = (x-2)(x² + 2x + 4), so (x³ - 8)/(x - 2) = x² + 2x + 4

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