Civil Services Prep

Prelims 2026 · CSAT / Quantitative Aptitude · Question 13

A toy T jumps forward or backward. In each forward jump, it moves 5' forward whereas in each backward jump, it moves 2' backward. If in 31 jumps, T moves exactly 15' forward, then what is the difference of the number of forward and backward jumps?<br/>

  1. 6
  2. 7
  3. 8
  4. 9

Answer

9

Let forward jumps = F and backward jumps = B. Then F + B = 31 and 5F - 2B = 15. Substituting B = 31 - F: 5F - 2(31 - F) = 15, so 7F = 77, hence F = 11 and B = 20. Difference = 20 - 11 = 9.

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