Ranks by gender composition: In a class of 60, girls are twice the number of boys. Kamal is 17th from the top, with 9 girls ahead of him. How many boys are ranked after Kamal?

Difficulty: Medium

Correct Answer: 12

Explanation:


Introduction / Context:
We combine overall gender counts with position data to compute how many boys trail Kamal.



Given Data / Assumptions:

  • Total = 60; girls are twice boys ⇒ boys = 20, girls = 40.
  • Kamal ranks 17th from top.
  • There are 9 girls ahead of Kamal.
  • Kamal is a boy (typical assumption for this named context).


Concept / Approach:
Among the 16 ahead of Kamal, boys_ahead = 16 − 9 = 7. Then boys_after = total_boys − boys_ahead − 1 (subtract Kamal himself).



Step-by-Step Solution:

Total boys = 20; boys ahead of Kamal = 7.Boys after Kamal = 20 − 7 − 1 = 12.


Verification / Alternative check:
Sanity: boys not ahead or Kamal himself must be behind, and 12 is consistent.



Why Other Options Are Wrong:
They arise from forgetting to subtract Kamal or miscounting boys among those ahead.



Common Pitfalls:
Assuming “girls twice boys” means “boys twice girls”; mixing total vs. ahead subsets.



Final Answer:
12

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