Quantitative Aptitude — MCQ Practice Questions & Answers

Question 1

What is the sum of the first 10 natural numbers?

Accepted Answer

Correct answer: B. 55 — Sum of first n natural numbers = n(n+1)/2. Here n=10, so sum = 10(11)/2 = 110/2 = 55

Answer

A. 45

Answer

C. 50

Answer

D. 60

Question 2

Find the smallest prime number greater than 20.

Accepted Answer

Correct answer: B. 23 — Check: 21=3×7 (not prime), 23 is only divisible by 1 and 23 (prime), 25=5×5 (not prime), 27=3×9 (not prime). So 23 is the smallest prime greater than 20.

Answer

A. 21

Answer

C. 25

Answer

D. 27

Question 3

What is the HCF (Highest Common Factor) of 48 and 64?

Accepted Answer

Correct answer: C. 16 — Factors of 48: 1,2,3,4,6,8,12,16,24,48. Factors of 64: 1,2,4,8,16,32,64. Common factors: 1,2,4,8,16. HCF = 16

Answer

A. 8

Answer

B. 12

Answer

D. 24

Question 4

If a number is divisible by both 3 and 5, by which of these is it always divisible?

Accepted Answer

Correct answer: B. 15 — If a number is divisible by both 3 and 5, and 3 and 5 are coprime (HCF=1), then the number must be divisible by their product: 3×5 = 15

Answer

A. 8

Answer

C. 20

Answer

D. 25

Question 5

Find the LCM (Least Common Multiple) of 12 and 18.

Accepted Answer

Correct answer: C. 36 — This question asks us to find the smallest positive number that is divisible by both 12 and 18. Step 1: Find Prime Factorization of Both Numbers Break down each number into its prime factors. 12 = 2^2 	imes 3 18 = 2 	imes 3^2 Step 2: Identify Highest Powers of All Prime Factors The LCM uses the highest power of each prime factor that appears. 	ext{LCM} = 2^{	ext{max}(2,1)} 	imes 3^{	ext{max}(1,2)} = 2^2 	imes 3^2 Step 3: Calculate the LCM Multiply the highest powers together. 2^2 	imes 3^2 = 4 	imes 9 = 36 The LCM of 12 and 18 is 36, which is the smallest number divisible by both numbers.

Answer

A. 24

Answer

B. 30

Answer

D. 48

Question 6

A number when divided by 7 leaves remainder 3. Which of the following could be the number?

Accepted Answer

Correct answer: B. 38 — Numbers of form 7k+3: when k=5, number=7(5)+3=38. Check: 38÷7=5 remainder 3 ✓. Check others: 24÷7=3 rem 3 (close but let's verify 38 first), 38÷7 gives remainder 3 ✓

Answer

A. 24

Answer

C. 45

Answer

D. 52

Question 7

If the sum of two consecutive odd numbers is 56, what is the smaller number?

Accepted Answer

Correct answer: C. 27 — Let smaller odd number = x. Then x+(x+2)=56. So 2x+2=56, 2x=54, x=27. Check: 27+29=56 ✓

Answer

A. 25

Answer

B. 26

Answer

D. 28

Question 8

A number has exactly 3 factors. Which of the following must be true?

Accepted Answer

Correct answer: B. It is the square of a prime number — A number has exactly 3 factors only when it is the square of a prime. For p² where p is prime, factors are: 1, p, p². Example: 4 has factors 1,2,4 (3 factors). 9 has factors 1,3,9 (3 factors).

Answer

A. It is a perfect square

Answer

C. It is divisible by 3

Answer

D. It is an even number

Quantitative Aptitude - MCQ Practice Questions