Multiple choice general knowledge math & puzzles

Two trains, 200 km apart, are moving toward each other at the speed of 50 km/hour each. A fly takes off from one train flying straight toward the other at the speed of 75 km/hour. Having reached the other train, the fly bounces off it and flies back to the first train. The fly repeats the trip until the trains collide and the bug is squashed.What distance has the fly traveled until its death?

  1. 160km

  2. 170km

  3. 150km

  4. 120km
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The key insight is that the fly keeps flying continuously until the trains collide. The trains start 200 km apart and approach each other at 50 km/h each, so their relative speed is 100 km/h. The collision time is 200 km ÷ 100 km/h = 2 hours. The fly travels at 75 km/h for those 2 hours, covering 75 × 2 = 150 km. The complex back-and-forth path is irrelevant - we only need total time and speed.

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