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Defence NDA / CDS
Mathematics

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

15 Q 4 Subjects 12th / Graduate
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Difficulty: All Easy Medium Hard 1–10 of 15
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Q.1 Easy Mathematics
cos 60° = ?
A 1/2
B √3/2
C 1
D 0
Correct Answer:  A. 1/2
EXPLANATION

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

Step 1: Recall the standard angle values

The trigonometric ratios for 0°, 30°, 45°, 60°, and 90° are fixed values that must be memorized for competitive exams.

Step 2: Identify cos 60° from the standard table

For 60°, the cosine value is:

\[\cos 60° = \frac{1}{2}\]
Step 3: Verify using the unit circle concept

At 60°, if you place a point on the unit circle, the x-coordinate (which represents cosine) equals \(\frac{1}{2}\).

Step 4: Eliminate other options

- \(\sin 60° = \frac{\sqrt{3}}{2}\) (option B is sine, not cosine)

- \(\cos 0° = 1\) (option C)

- \(\cos 90° = 0\) (option D)

Therefore, \(\cos 60° = \frac{1}{2}\)

The correct answer is A) 1/2

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Q.2 Easy Mathematics
HCF of 24 and 36?
A 6
B 8
C 12
D 18
Correct Answer:  C. 12
EXPLANATION

HCF (Highest Common Factor) is the largest number that divides both given numbers without leaving a remainder.

Step 1: Find all factors of 24

Factors of 24 = 1, 2, 3, 4, 6, 8, 12, 24

Step 2: Find all factors of 36

Factors of 36 = 1, 2, 3, 4, 6, 9, 12, 18, 36

Step 3: Identify common factors

Common factors = 1, 2, 3, 4, 6, 12

Step 4: Select the highest common factor

The largest common factor = 12

Alternative Method - Using Prime Factorization:

24 = 2³ × 3

36 = 2² × 3²

HCF = 2² × 3 = 4 × 3 = 12

Therefore, HCF of 24 and 36 = 12

The answer is (C) 12

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Q.3 Easy Mathematics
Slope of y = 3x + 5?
A 5
B 3
C -3
D -5
Correct Answer:  B. 3
EXPLANATION

The slope of a line is the coefficient of x in the standard linear equation form y = mx + c.

Step 1: Identify the standard form of a linear equation.

The equation of a line is written as: y = mx + c, where m is the slope and c is the y-intercept.

Step 2: Compare the given equation with standard form.

Given equation: y = 3x + 5

Standard form: y = mx + c

Step 3: Extract the slope.

Here, m = 3 (coefficient of x) and c = 5 (constant term)

Therefore, the slope is 3.

The answer is (B) 3

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Q.4 Easy Mathematics
Probability of head in coin toss?
A 1/4
B 1/3
C 1/2
D 2/3
Correct Answer:  C. 1/2
EXPLANATION

When flipping a fair coin, the probability of any single outcome equals the number of favorable outcomes divided by total possible outcomes.

Step 1: Identify total possible outcomes when tossing a coin.

A coin has exactly 2 possible outcomes: Head or Tail.

Step 2: Identify favorable outcomes for getting a head.

Number of ways to get a Head = 1

Step 3: Apply probability formula.
\[\text{Probability} = \frac{\text{Number of favorable outcomes}}{\text{Total number of possible outcomes}}\]
Step 4: Calculate.
\[P(\text{Head}) = \frac{1}{2}\]

Therefore, the probability of getting a head in a coin toss is \(\frac{1}{2}\) or 0.5 or 50%.

The answer is C) 1/2

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Q.5 Easy Mathematics
√144 = ?
A 11
B 12
C 13
D 14
Correct Answer:  B. 12
EXPLANATION

Square root is the inverse operation of squaring, and asks: what number multiplied by itself equals 144?

Step 1: Understand what √144 means

We need to find a number that when multiplied by itself gives 144.

Step 2: Check which number squared equals 144

We test the options by squaring them:

- 11² = 11 × 11 = 121 (not 144)

- 12² = 12 × 12 = 144 (matches!)

- 13² = 13 × 13 = 169 (not 144)

- 14² = 14 × 14 = 196 (not 144)

Step 3: Verify the answer

Since 12 × 12 = 144, we have √144 = 12

Therefore, the answer is (B) 12

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Q.6 Easy Mathematics
f(x)=x²+3x+2. f(2)=?
A 10
B 12
C 8
D 6
Correct Answer:  B. 12
EXPLANATION

To find f(2), substitute x = 2 into the given function and calculate the result.

Step 1: Write the function.
\[f(x) = x^2 + 3x + 2\]
Step 2: Substitute x = 2 into the function.
\[f(2) = (2)^2 + 3(2) + 2\]
Step 3: Calculate the square term.
\[f(2) = 4 + 3(2) + 2\]
Step 4: Calculate the multiplication term.
\[f(2) = 4 + 6 + 2\]
Step 5: Add all terms.
\[f(2) = 12\]

Therefore, f(2) = 12

The answer is B) 12

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Q.7 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.8 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.9 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.10 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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