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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 1191–1200 of 1,216
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Q.1191 Medium Mathematics
Integrate ∫2x dx?
A x²+C
B 2x²+C
C x+C
D 2x+C
Correct Answer:  A. x²+C
EXPLANATION

Integration is the reverse process of differentiation, and we use the power rule to find antiderivatives.

Step 1: Identify the integral form

We need to find ∫2x dx, which means we're integrating the function 2x with respect to x.

Step 2: Apply the power rule of integration

The power rule states: ∫x^n dx = \(\frac{x^{n+1}}{n+1}\) + C

Rewrite 2x as: ∫2x^1 dx

Step 3: Factor out the constant

∫2x dx = 2∫x^1 dx

Step 4: Apply the power rule
\[2∫x^1 dx = 2 \times \frac{x^{1+1}}{1+1} + C = 2 \times \frac{x^2}{2} + C = x^2 + C\]
Step 5: Verify by differentiation

\(\frac{d}{dx}\)(x² + C) = 2x ✓

Therefore, ∫2x dx = x² + C

Answer: (A) x²+C

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Q.1192 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.1193 Medium Mathematics
45° in radians?
A π/4
B π/3
C π/2
D π/6
Correct Answer:  A. π/4
EXPLANATION

To convert degrees to radians, use the conversion formula that relates the two angle measurement systems.

Step 1: Recall the conversion formula from degrees to radians.
\[\text{Radians} = \text{Degrees} \times \frac{\pi}{180°}\]
Step 2: Substitute 45° into the formula.
\[\text{Radians} = 45° \times \frac{\pi}{180°}\]
Step 3: Simplify the fraction.
\[= \frac{45\pi}{180} = \frac{\pi}{4}\]

Therefore, 45° = \(\frac{\pi}{4}\) radians.

The answer is (A) π/4

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Q.1194 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.1195 Medium Mathematics
7! (7 factorial) = ?
A 2520
B 5040
C 720
D 1260
Correct Answer:  B. 5040
EXPLANATION

Factorial is the product of all positive integers from 1 up to a given number.

Step 1: Understand factorial notation

7! means 7 × 6 × 5 × 4 × 3 × 2 × 1

Step 2: Multiply step by step
\[7! = 7 \times 6 \times 5 \times 4 \times 3 \times 2 \times 1\]
Step 3: Calculate from left to right

7 × 6 = 42

42 × 5 = 210

210 × 4 = 840

840 × 3 = 2520

2520 × 2 = 5040

5040 × 1 = 5040

Therefore, 7! = 5040

The answer is (B) 5040

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Q.1196 Medium Mathematics
Solve: x² - 5x + 6 = 0
A x=2,3
B x=1,6
C x=3,4
D x=2,4
Correct Answer:  A. x=2,3
EXPLANATION

This question asks you to find the roots of a quadratic equation using factorization.

Step 1: Write the equation in standard form.
\[x^2 - 5x + 6 = 0\]
Step 2: Find two numbers that multiply to give 6 (constant term) and add to give -5 (coefficient of x).

The numbers are -2 and -3, because:

(-2) × (-3) = 6

(-2) + (-3) = -5

Step 3: Factorize the quadratic.
\[(x - 2)(x - 3) = 0\]
Step 4: Solve for x by setting each factor equal to zero.

x - 2 = 0 → x = 2

x - 3 = 0 → x = 3

Step 5: Verify by substituting back.

For x = 2: (2)² - 5(2) + 6 = 4 - 10 + 6 = 0 ✓

For x = 3: (3)² - 5(3) + 6 = 9 - 15 + 6 = 0 ✓

Therefore, x = 2, 3

The answer is (A).

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Q.1197 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.1198 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.1199 Medium Mathematics
Differentiate y = 3x²
A 6x
B 3x
C 6x²
D 3x²
Correct Answer:  A. 6x
EXPLANATION

Differentiation is finding the rate of change of a function with respect to a variable.

Step 1: Identify the function and the rule to apply.

We have y = 3x² and we need to use the Power Rule of differentiation.

Step 2: Recall the Power Rule.

The Power Rule states: If y = ax^n, then \(\frac{dy}{dx} = n \cdot a \cdot x^{n-1}\)

Step 3: Apply the Power Rule to our function.

Here, a = 3 and n = 2

\[\frac{dy}{dx} = 2 \cdot 3 \cdot x^{2-1}\]
Step 4: Simplify.
\[\frac{dy}{dx} = 6 \cdot x^1 = 6x\]

Therefore, the derivative of y = 3x² is 6x

Answer: A) 6x

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Q.1200 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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