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An integer x, with 10 <= x <= 99, is to be chosen. If all choices are equally likely, what is the probability that at least one digit of x is a 7?

 Jul 5, 2019
edited by Guest  Jul 5, 2019
edited by Guest  Jul 5, 2019
edited by Guest  Jul 5, 2019
 #1
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We have   99 - 10 + 1  =  90 possible integers

 

The ones that contain at least one "7"   are

17, 27, 37, 47, 57, 67, 70 - 79, 87, 97   =  18 integers

 

So....the probability of selecting an integer with one with at least one "7"  is

 

18 / 90  =

 

1/5

 

 

 

cool cool cool

 Jul 5, 2019

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