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 10 cell phones and 10 numbers (Posted on 2008-06-11)
You are given 10 cell phones and 10 cell numbers(each number corresponds to one of each of those 10 cell phones), but you don't know which number corresponds to which cell phone. Your task is to label each cell phone with its corresponding number. Using optimal procedures, what is the probability that you will finish the task in exactly 5 attempts?

A single attempt is defined as calling a number from a cell phone.

Hint: The caller's number will be displayed in the cell that is being called.

 See The Solution Submitted by Praneeth Rating: 4.2500 (4 votes)

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 re: Solution? | Comment 2 of 10 |
(In reply to Solution? by Josie Faulkner)

I think you missed the fact that you might be calling the same cell phone you are using.

Chance of callig different cell phone (not the one you are dialing from)

Call #1 = 9/10

Call#2 = 7/8

Call#3 = 5/6

Call#4 = 3/4

Call#5 = 1/2

9/10*7/8*5/6*3/4*1/2 = 0,2461...

Guess this is it.

Call

 Posted by Fernando on 2008-06-11 18:09:46

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