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# confusion of both questions..

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Hi, I know Im not suppsoed to do 2 questions per forum however I dont know the difference between these two problems and why the calculation process at the end is different from each other.

1) A tennis ball is shot vertically to a height of 20 feet and aloowed to drop. Each bounce is 80% as high as the previous bounce. What is the total distance the ball travels from when it is shot unit it bounces the fourth time?

2) Suppose you drop a tennis ball from a height of 15 feet. After the ball hits the floor, it rebounds to 85% of its previous height. What is the total distance the ball traveled.

May 22, 2022

#1
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Hi Jenny

1) A tennis ball is shot vertically to a height of 20 feet and aloowed to drop. Each bounce is 80% as high as the previous bounce. What is the total distance the ball travels from when it is shot unit it bounces the fourth time?

0.8*20=16

0.8*16=12.8

etc

so

Up distance = 20+16+12.8+.....    sum to infinity

down distance = 20+16+12.8+ ....sum to infinity

2) Suppose you drop a tennis ball from a height of 15 feet. After the ball hits the floor, it rebounds to 85% of its previous height. What is the total distance the ball traveled.

15*0.85=12.75

12.65*0.85=10.8375

down distance = 15+12.75+10.8375+ ... sum to infinity

up distance = 12.75+10.8375+.... sum to infinity

use GP sum of infinite series to get the first answers.

Is that enough help?

May 22, 2022
#2
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yes thank you I understand it a lot better now May 22, 2022
#3
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Very glad to hear it Melody  May 22, 2022