Number System

JKSSB Sub-Inspector (Executive) · Mathematics · 97 practice questions with answers and explanations: 35 Easy, 34 Medium, 28 Hard.

Sample questions

Sample Easy question 1

Which of the following is a prime number: 91, 93, 95, 97?

  1. 91
  2. 93
  3. 95
  4. 97
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Answer: D. 91=7×13, 93=3×31, 95=5×19, but 97 has no factors other than 1 and itself.

Sample Medium question 2

Find the number of trailing zeros at the end of 25!.

  1. 4
  2. 5
  3. 6
  4. 7
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Answer: C. Trailing zeros = ⌊25/5⌋ + ⌊25/25⌋ = 5 + 1 = 6.

Sample Hard question 3

The product of two numbers is 3600 and their HCF is 20. Find their LCM.

  1. 174
  2. 177
  3. 180
  4. 183
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Answer: C. LCM = 3600/20 = 180.

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