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probability question

by nagar.sandeep » Thu Sep 30, 2010 9:00 am
hi,

please explain the solution to the following question:
I am not sure whether this question is valid or not, kindly excuse me if its an invalid one.



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 ?
a. 1/6
b. 1/5
c. 1/3
d. 2/5
e. 2/3

Thanks,
Sandeep
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by narik11 » Thu Sep 30, 2010 9:18 am
nagar.sandeep wrote:hi,

please explain the solution to the following question:
I am not sure whether this question is valid or not, kindly excuse me if its an invalid one.



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 ?
a. 1/6
b. 1/5
c. 1/3
d. 2/5
e. 2/3

Thanks,
Sandeep
number of possibilities for sum of the numbers on the cards to be 8: 5
(2,6) (6,2) (3,5) (5,3) (4,4)

so its 2/5
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by GMATGuruNY » Thu Sep 30, 2010 9:22 am
nagar.sandeep wrote:hi,

please explain the solution to the following question:
I am not sure whether this question is valid or not, kindly excuse me if its an invalid one.



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 ?
a. 1/6
b. 1/5
c. 1/3
d. 2/5
e. 2/3

Thanks,
Sandeep
P = good outcomes/total possible outcomes

Total number of ways to get a sum of 8:
2, 6
3, 5
4, 4
5, 3
6, 2
So total = 5.

Good outcomes:
3, 5
5, 3
So good = 2

Good/Total = 2/5
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