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Defence NDA / CDS

NDA & CDS MCQ questions — Mathematics, English, GK, Reasoning for defence exams.

1,216 Q 4 Subjects 12th / Graduate
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Difficulty: All Easy Medium Hard 1201–1210 of 1,216
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Q.1201 Medium Mathematics
Median of: 5,8,3,9,1,7,6?
A 6
B 5
C 7
D 8
Correct Answer:  A. 6
EXPLANATION

To find the median, we must first arrange all numbers in ascending order, then locate the middle value.

Step 1: Count the total numbers

We have 7 numbers: 5, 8, 3, 9, 1, 7, 6

Step 2: Arrange in ascending order

1, 3, 5, 6, 7, 8, 9

Step 3: Find the position of median

Since n = 7 (odd number), median position = \(\frac{n+1}{2} = \frac{7+1}{2} = 4\)

Step 4: Identify the 4th element

Counting from left: 1st is 1, 2nd is 3, 3rd is 5, 4th is 6

Therefore, the median is 6.

The answer is (A) 6

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Q.1202 Easy Mathematics
log₁₀(1000) = ?
A 2
B 3
C 4
D 10
Correct Answer:  B. 3
EXPLANATION

Logarithm is the inverse operation of exponentiation; \(\log_b(x) = y\) means \(b^y = x\).

Step 1: Understand what we need to find.

We need to find the value of \(\log_{10}(1000)\). This asks: "10 raised to what power equals 1000?"

Step 2: Express 1000 as a power of 10.
\[1000 = 10 \times 10 \times 10 = 10^3\]
Step 3: Apply the logarithm definition.

Since \(10^3 = 1000\), we have:

\[\log_{10}(1000) = 3\]

Therefore, \(\log_{10}(1000) = 3\)

The answer is (B) 3

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Q.1203 Easy Mathematics
Sum of angles in a triangle?
A 90°
B 180°
C 270°
D 360°
Correct Answer:  B. 180°
EXPLANATION

The sum of all three interior angles of any triangle is always constant, regardless of the triangle's shape or size.

Step 1: Understand the fundamental property

Every triangle has exactly 3 interior angles. These angles are formed where two sides of the triangle meet.

Step 2: Apply the angle sum theorem

The angle sum property of a triangle states:

\[\text{Angle 1} + \text{Angle 2} + \text{Angle 3} = 180°\]
Step 3: Verify with examples

- Equilateral triangle: 60° + 60° + 60° = 180°

- Right triangle: 90° + 45° + 45° = 180°

- Isosceles triangle: 70° + 70° + 40° = 180°

This property holds for all triangles without exception. It's a basic axiom in Euclidean geometry.

Therefore, the sum of angles in a triangle = 180°

Answer: B) 180°

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Q.1204 Easy Mathematics
Area of circle with radius 7cm (π=22/7)?
A 154 sq cm
B 144 sq cm
C 164 sq cm
D 174 sq cm
Correct Answer:  A. 154 sq cm
EXPLANATION

To find the area of a circle, we use the formula Area = πr², where r is the radius.

Step 1: Write the formula for area of a circle.
\[A = \pi r^2\]
Step 2: Substitute the given values.

- Radius r = 7 cm

- π = 22/7

\[A = \frac{22}{7} \times 7^2\]
Step 3: Calculate 7².
\[A = \frac{22}{7} \times 49\]
Step 4: Simplify by canceling 7.
\[A = 22 \times 7 = 154 \text{ sq cm}\]

Therefore, the area of the circle is 154 sq cm.

The answer is (A) 154 sq cm.

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Q.1205 Easy Mathematics
Solve: 2x + 5 = 15
A x=4
B x=5
C x=6
D x=3
Correct Answer:  B. x=5
EXPLANATION

This is a linear equation problem where we need to isolate the variable x on one side.

Step 1: Start with the equation
\[2x + 5 = 15\]
Step 2: Subtract 5 from both sides to remove the constant term
\[2x + 5 - 5 = 15 - 5\]
\[2x = 10\]
Step 3: Divide both sides by 2 to isolate x
\[\frac{2x}{2} = \frac{10}{2}\]
\[x = 5\]
Step 4: Verify by substituting x = 5 back into the original equation

\[2(5) + 5 = 10 + 5 = 15\] ✓

Therefore, x = 5

The answer is B) x = 5

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Q.1206 Easy Mathematics
sin 30° = ?
A 1
B 0.5
C √3/2
D 1/√2
Correct Answer:  B. 0.5
EXPLANATION

This question tests your knowledge of standard trigonometric ratios for common angles.

Step 1: Recall the standard trigonometric ratios table for common angles (0°, 30°, 45°, 60°, 90°).
Step 2: Locate the value of sin 30° from the standard table:
\[\sin 30° = \frac{1}{2} = 0.5\]
Step 3: Verify using the unit circle or right triangle approach — in a 30-60-90 triangle, the side opposite to 30° is half the hypotenuse, giving us \(\sin 30° = \frac{1}{2}\).
Step 4: Convert the fraction to decimal form:
\[\frac{1}{2} = 0.5\]

Therefore, sin 30° = 0.5

Answer: B) 0.5

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Q.1207 Easy Mathematics
In triangle ABC, point D lies on BC such that AD is the angle bisector. If AB = 6 cm, AC = 9 cm, and BD = 4 cm, what is the length of DC?
A 5 cm
B 6 cm
C 7 cm
D 8 cm
Correct Answer:  B. 6 cm
EXPLANATION

By the Angle Bisector Theorem, the angle bisector divides the opposite side in the ratio of the adjacent sides.

Therefore, BD/DC = AB/AC, which gives 4/DC = 6/9.

Solving: DC = (4 × 9)/6 = 36/6 = 6 cm.

This theorem is essential for solving numerous geometry problems in competitive exams.

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Q.1208 Medium Mathematics
A regular hexagon is inscribed in a circle of radius 6 cm. What is the difference between the perimeter of the hexagon and the circumference of the circle?
A 36 - 12π cm
B 12π - 36 cm
C 36 - 6π cm
D 6π - 36 cm
Correct Answer:  B. 12π - 36 cm
EXPLANATION

For a regular hexagon inscribed in a circle of radius R, the side length equals R.

Here, side = 6 cm, so perimeter = 6 × 6 = 36 cm.

The circumference of the circle = 2πR = 12π cm.

Since 12π ≈ 37.7 > 36, the difference is 12π - 36 cm (circumference is greater).

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Q.1209 Medium Mathematics
Two concentric circles have radii r and R (where r < R). The area of the ring formed between them is equal to the area of the inner circle. What is the ratio R:r?
A √2:1
B 2:1
C √3:1
D 3:1
Correct Answer:  A. √2:1
EXPLANATION

The area of the ring = π(R² - r²).

Given that this equals the area of the inner circle = πr², we have R² - r² = r², which gives R² = 2r², so R = r√2.

Therefore, the ratio R:r = √2:1.

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Q.1210 Easy Mathematics
In a right-angled triangle, the altitude drawn to the hypotenuse divides it into segments of lengths 9 cm and 16 cm. What is the length of the altitude?
A 12 cm
B 15 cm
C 18 cm
D 20 cm
Correct Answer:  A. 12 cm
EXPLANATION

By the geometric mean altitude theorem, when an altitude is drawn to the hypotenuse of a right triangle, the altitude is the geometric mean of the two segments of the hypotenuse.

Therefore, altitude = √(9 × 16) = √144 = 12 cm.

This is a fundamental property used frequently in competitive exams.

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