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: (B) 5

The ball is dropped from 150 cm: 1st ground hit (bounces to $150$$\times$ 4/5 = 120 $\text{ cm}$); 2nd hit (bounces to $120$$\times$ 4/5 = 96 $\text{ cm}$); 3rd hit (bounces to $96$$\times$ 4/5 = 76.8 $\text{ cm}$); 4th hit (bounces to $76.8$$\times$ 4/5 = 61.44 $\text{ cm}$); 5th hit (bounces to $61.44$$\times$ 4/5 = 49.152 $\text{ cm}$). Since 49.152 cm is less than 50 cm, the ball does not bounce further. Thus, the ball hits the ground 5 times.