Peter hits 2 shots right for every 5 shots what is the probability of Peter winning the game


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John and Peter compete against each other in shooting. Proba [#permalink]

  26 Oct 2019, 17:55

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Question Stats:

47% [02:21] correct
53% [02:30] wrong
based on 32 sessions

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John and Peter compete against each other in shooting. Probability of John hitting the target is 0.4 and Probability of Peter hitting the target is 0.7. If John has the first shot, post which they strike alternately and game ends when someone hits the target first. What is the probability that John wins?

A. 8/13
B. 15/22
C. 20/41
D. 2/5
E. 3/25

Posted from my mobile device

Math Expert

Joined: 02 Aug 2009

Posts: 10596

John and Peter compete against each other in shooting. Proba [#permalink]

  26 Oct 2019, 18:37

Dillesh4096 wrote:

John and Peter compete against each other in shooting. Probability of John hitting the target is 0.4 and Probability of Peter hitting the target is 0.7. If John has the first shot, post which they strike alternately and game ends when someone hits the target first. What is the probability that John wins?

A. 8/13
B. 15/22
C. 20/41
D. 2/5
E. 3/25

Posted from my mobile device


John can win when he hits the target but Peter misses it in previous attempts..
John can win in first shot of the game =0.4
or third shot of the game, when peter misses the second one = [1-0.4][1-0.7]0.4 =0.6*0.7*0.4 and so on...

Over all probability = \[0.4+0.6*0.3*0.4+0.6*0.3*0.6*0.3*0.4...=0.4[1+0.6*0.3+[0.6*0.3]^2+....]\]
So what we have in the bracket is a geometrical progression with each term increasing by 0.6*0.3 over the preceding term

Sum = \[0.4[\frac{a}{1-r}]=0.4[\frac{1}{1-0.18}]=0.4*\frac{1}{0.82}=\frac{40}{82}=\frac{20}{41}\]

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Re: John and Peter compete against each other in shooting. Proba [#permalink]

  30 Oct 2019, 08:04

The question statement is ambiguous.

Re: John and Peter compete against each other in shooting. Proba [#permalink]

30 Oct 2019, 08:04

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