Number System aptitude questions
Number System questions are part of the Quant section of placement aptitude tests. Reduce the question to prime factors before testing divisibility. Below are 5 worked examples with the answer and the working; practise ten fresh ones or take a timed mock when you are ready.
Example 1. How many factors does 12005 have?
- A. 12
- B. 5
- C. 10 (answer)
- D. 4
Write 12005 = 7^4 * 5^1. The number of factors is (4 + 1) * (1 + 1) = 10.
Example 2. What is the remainder when 27472 is divided by 9?
- A. 4 (answer)
- B. 9
- C. 3
- D. 5
A number and its digit sum have the same remainder on division by 9. The digit sum of 27472 is 22, and the division leaves 4.
Example 3. The HCF of two numbers is 5 and the numbers are 20 and 25. What is their LCM?
- A. 100 (answer)
- B. 45
- C. 5
- D. 500
For two numbers, HCF * LCM = product of the numbers, so LCM = (20 * 25)/5 = 100.
Example 4. The HCF of two numbers is 3 and the numbers are 21 and 24. What is their LCM?
- A. 168 (answer)
- B. 45
- C. 504
- D. 3
For two numbers, HCF * LCM = product of the numbers, so LCM = (21 * 24)/3 = 168.
Example 5. What is the remainder when 28256 is divided by 11?
- A. 11
- B. 8 (answer)
- C. 4
- D. 3
For 11, add and subtract alternate digits; the difference gives the remainder. The digit sum of 28256 is 23, and the division leaves 8.
More Quant practice elsewhere: IndiaBIX, GeeksforGeeks. See the 60-day aptitude plan.