A boy plays with a ball and he drops it from a height of 1.5 m. Every time the ball hits the ground, it bounces back to attain a height 4/5 th of the previous height. The ball does not bounce further if the previous height is less than 50 cm. What is the number of times the ball hits the ground before the ball stops bouncing ?
6
Given:
Ball is dropped from a height of 1.5 m
The ball bounces back to 4/5 th of the previous height and if the height is less than 50 cm then it does not bounce back.
Calculation:
Initial height of the drop = 1.5 m = 150 cm
| Drop | Previous Height(cm) | Height after Bouncing Back(cm) |
| 1 | 150 | 150 × 4/5 = 120 |
| 2 | 120 | 120 × 4/5 = 96 |
| 3 | 96 | 96 × 4/5 = 76.8 |
| 4 | 76.8 | 76.8 × 4/5 = 61.44 |
| 5 | 61.44 | 61.44 × 4/5 = 49.152 |
| 6 | 49.152 | 0 |
So, the ball touches the ground for 6 times.
Hence, option 3 is correct.
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