GWD Math 20 Q14

needthat

Help pls. I am sorry that I can't type in Chinese.

I got 1/16 while the right answer is 2/5.
6x6=36 and the ones with one 5 is (3, 5 ) and (5,3
Thanks a lot!
Q14:

Six cards numbered from 1 to 6 are placed in an empty bowl.First one card is drawn and then put back into the bowl; then a second card is drawn.If the cards are drawn at random and if the sum of the numbers on the cards is 8, what is the probability that one of the two cards drawn is numbered 5 ?

guosimonqq

The question has said the sum of the numbers is 8, so the denominator is not 6*6,but 5 for there are five conditions: (2,6),(6,2),(4,4),(5,3),(3,5). Among the five, only two are suitable. So the answer is 2/5.

needthat

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