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A ball is dropped gently from a height of 120 m. Each time it hits the ground, it rises to (4)/(5) of the height from which it fell. What is the total distance covered by the ball before it finally comes to rest?

1. 960 m
2. 1000 m
3. 1080 m
4. Infinite

Correct answer: 1080 m

Solution

First fall is 120 m; each subsequent up-and-down is a geometric series. Total = 120 + 2(120)(4/5)/(1-4/5) = 120 + 960 = 1080 m.

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