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Unformatted text preview: git and units digit (i.e. 33 or 51 or 03) each of them represent a number from 1 to 99 (for 01 =
1).
So after we know we have XX and we know that the total number of integers is 100 (from1 to 100
including). All we have to do is to find the probability that the second X in XX will be 5 and to multiply this
probability in the number of integers given (i.e. N = 100).
For the second X we can only choose the number 5 from ten digits (09) so the probability is 1/10. The
probability for forming a number that has a unit digit of 5 is P = 1/10.
And using the probability method
P*N = 100*1/10 = 10. The answer is (C).
As you can see the basic method is easier than the probability method but this is only true in simple
problems. As the problems get more and more complex it will be harder to solve them in the time frame of
two minutes in any method other than...
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This document was uploaded on 02/28/2014.
 Fall '13

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