SOLUTION: Subjects for the next presidential election poll are contacted using telephone numbers in which the last four digits are randomly selected​ (with replacement). Find the probabili

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Question 1132477: Subjects for the next presidential election poll are contacted using telephone numbers in which the last four digits are randomly selected​ (with replacement). Find the probability that for one such phone​ number, the last four digits include at least one 0.
The probability is ?
Answer by ikleyn(52767) About Me  (Show Source):
You can put this solution on YOUR website!
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ANSWER.   The probability is   %2810%5E4-9%5E4%29%2F10%5E4 = 0.3439 = 34.39%.


SOLUTION 

10%5E4  is the number of all possible phone numbers consisting of 4 digits from 0 to 9 inclusively.


9%5E4  is the number of all possible phone numbers consisting of 4 digits from 1 to 9 inclusively  
     (that do not include  0 (zero) among the 4 digits).


The difference  10%5E4 - 9%5E4 is the number of those 4 digit phone numbers that include at least one 0 (zero).


The ratio  %2810%5E4-9%5E4%29%2F10%5E4  is the probability you are looking for.

Solved,  explained and completed.