Single correct option
In a 1 km race, A beats B by 100 m and B beats C by 100 m. By how many metres does A beat C in a 1 km race? (Assume all run at constant speeds.)
- A. 210 m
- B. 190 m
- C. 200 m
- D. 180 m
Show answer and solution
Answer: (B) 190 m
When A runs 1000 m, B runs 900 m. When B runs 1000 m, C runs 900 m, so C's speed is 0.9 × B's speed.
When A runs 1000 m, B runs 900 m, and C runs 0.9 × 900 = 810 m.
A beats C by 1000 − 810 = 190 m.
Trap: 200 m assumes the two margins simply add, but B's lead over C is measured over B's full 1000 m, not over the 900 m B covers in A's race.
When A runs 1000 m, B runs 900 m, and C runs 0.9 × 900 = 810 m.
A beats C by 1000 − 810 = 190 m.
Trap: 200 m assumes the two margins simply add, but B's lead over C is measured over B's full 1000 m, not over the 900 m B covers in A's race.
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