OK, i have had many problems like this, and i still don\'t knowhow to do it! Sup

Question

OK, i have had many problems like this, and i still don't knowhow to do it! Suppose you are getting a new telephone installed. What is theprobabiliy that the final three digits in the telephone number willall be even? (ex: _ _ _-_ _ _-_ _ _ _ ) the three in redare even...what prob? OK, i have had many problems like this, and i still don't knowhow to do it! Suppose you are getting a new telephone installed. What is theprobabiliy that the final three digits in the telephone number willall be even? (ex: _ _ _-_ _ _-_ _ _ _ ) the three in redare even...what prob?

Explanation / Answer

This is another approach: In the denominator, for each of the 10 digits,there are 10 choices. So, there are 10x10x10x.......x10 = 10^10ways Now in the numerator, for each of first 7digits there are 10 choices and for each of the last 3 digits thereare only 5 choices because there are only 5 possible even numbers.So, there are 10x10x10x10x10x10x10x5x5x5 = (10^7)(5^3) Thus, probability = (10^7)(5^3)/(10^10) =(5^3)/(10^3) = 1/8

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