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HKIMO 2026 Grade 9 National Preliminary Set 03 Question 24

HKIMO · HKIMO 2026 Grade 9 National Preliminary Set 03

Question 24

A box contains three black balls and five red balls. In how many ways can three balls be drawn simultaneously with exactly one black ball?

Editorial counting convention: distinguish the individual physical balls, including balls of the same colour.
  1. 60
  2. 30
  3. 20
  4. 10