Selected MCQ

Current Question
A number is divisible by 3 and 5. It must be divisible by ____.
  • A. 8
  • B. 10
  • C. 15
  • D. 20
Correct Answer: C
Explanation:
LCM of 3 and 5.
Related Question 1
The smallest number which when increased by 1 is divisible by 12, 18, 24 and 32 is ____.
  • A. 1439
  • B. 1440
  • C. 1459
  • D. 1449
Correct Answer: A
Explanation:
LCM − 1 = required number.
Related Question 2
A number is selected at random from the first 50 natural numbeRs. What is the probability that it is divisible by 3 or 5?
  • A. 21/25
  • B. 17/25
  • C. 4/25
  • D. 8/25
Correct Answer: B
Explanation:
Count the multiples and apply the inclusion-exclusion principle → 34/50 = 17/25.
Related Question 3
12 children take 16 days to finish work. Time for the same work with a different number is ____.
  • A. 3 days
  • B. 4 days
  • C. 6 days
  • D. 8 days
Correct Answer: C
Explanation:
Work is inversely proportional.
Related Question 4
Three numbers are co-prime. The product of the first two is 551. Find the third.
  • A. 75
  • B. 81
  • C. 85
  • D. 89
Correct Answer: C
Explanation:
Factorization approach.
Related Question 5
Three flags of different coloRs. Number of signals using 1 or more flags is ____.
  • A. 6
  • B. 9
  • C. 15
  • D. 18
Correct Answer: C
Explanation:
Total combinations excluding empty = 2³ −1.