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JEE Main MCQ questions — Mathematics, Physics, Chemistry for engineering entrance.

487 Q 3 Subjects 12th (PCM)
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Q.11 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.12 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.13 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.14 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.15 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.16 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.17 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.18 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.19 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.20 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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