You drop a ball from a stair case that is 36 ft high. By the time you get down the stairs to measure the height of the bounce, the ball has bounced four times and has a height of 2.25 ft after its fourth bounce. How high did the ball bounce after it first hit the floor?

Question

Mathematics

Ruth Wang

3 September, 03:44

You drop a ball from a stair case that is 36 ft high. By the time you get down the stairs to measure the height of the bounce, the ball has bounced four times and has a height of 2.25 ft after its fourth bounce. How high did the ball bounce after it first hit the floor?

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Answers (1)

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Danny Mack · Answer 1

18 feet

Step-by-step explanation:

After each bounce, the ball reaches only a percentage of the maximum height it reached before.

The first height is 36 feet, after the first bounce, it will be 36*r, where r is the ratio of the height the ball can still reach by the previous maximum height.

In the second bounce, the height is 36*r^2

In the third bounce, the height is 36*r^3

In the fourth bounce, the height is 36*r^4, and this value is 2.25 ft, so:

36*r^4 = 2.25

r^4 = 2.25/36

r^4 = 0.0625

r = 0.5

So, after the first bounce, the height is:

36*r = 36*0.5 = 18 feet