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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 4/5th 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 ?

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 4/5th 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 ? Correct Answer 6

Given:

Ball is dropped from a height of 1.5 m

The ball bounces back to 4/5th 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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