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What is the probability that the sum will equal 9??

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by gmatpup » Mon Nov 21, 2011 4:24 am
A = {2, 3, 4, 5}

B= {4, 5, 6, 7, 8}

Two integers will be randomly selected from the sets above, one integer from set A and one integer from set B. WHat is the probability that the sum of the two integers will equal 9?

A. 0.15
B. 0.20
C. 0.25
D. 0.30
E. 0.33

Answer is B


Can someone please tell me how to approach questions such as this? Thanks so much!! :)
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by Anurag@Gurome » Mon Nov 21, 2011 4:43 am
gmatpup wrote:A = {2, 3, 4, 5}

B= {4, 5, 6, 7, 8}

Two integers will be randomly selected from the sets above, one integer from set A and one integer from set B. WHat is the probability that the sum of the two integers will equal 9?

A. 0.15
B. 0.20
C. 0.25
D. 0.30
E. 0.33

Answer is B


Can someone please tell me how to approach questions such as this? Thanks so much!! :)
There are total 20 ways to sum.
4 of the sums equals 9.
so, the required probability = 4/20 = 1/5 = .20

The correct answer is B.
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by chaitanyabhansali » Tue Nov 22, 2011 11:41 am
Anurag@Gurome wrote:
gmatpup wrote:A = {2, 3, 4, 5}

B= {4, 5, 6, 7, 8}

Two integers will be randomly selected from the sets above, one integer from set A and one integer from set B. WHat is the probability that the sum of the two integers will equal 9?

A. 0.15
B. 0.20
C. 0.25
D. 0.30
E. 0.33

Answer is B


Can someone please tell me how to approach questions such as this? Thanks so much!! :)
No. of ways of selecting one number from set A = 4C1 = 4
No. of ways of selecting one number from set B = 5C1 = 5

Total Ways = 4 * 5 = 20

There are 4 ways in which the sum is 9
1) 2(from A) + 7(from B) = 9
2) 3(from A) + 6(from B) = 9
3) 4(from A) + 5(from B) = 9
4) 5(from A) + 4(from B) = 9

Therefore, required probabiity = 4/20 = 0.2
IMO: B
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by tuanquang269 » Tue Nov 22, 2011 8:29 pm
4 x 5 = 20 ways to choose couple of number each from set A and B

There are 4 couple have sum of 9 include: (2,7) (3,6) (4,5) (5,4)

Probability = 4/20 = 20%
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by MBA.Aspirant » Wed Nov 23, 2011 1:15 am
gmatpup wrote:A = {2, 3, 4, 5}

B= {4, 5, 6, 7, 8}


Two integers will be randomly selected from the sets above, one integer from set A and one integer from set B. WHat is the probability that the sum of the two integers will equal 9?

A. 0.15
B. 0.20
C. 0.25
D. 0.30
E. 0.33

Answer is B


Can someone please tell me how to approach questions such as this? Thanks so much!! :)
Total events = 4 * 5= 20

favorable events = 4 (2+7), (5+4), (4+5), (3+6)

probability = 4/20 = 0.2 (B)
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by sk8legend408 » Wed Nov 23, 2011 5:28 am
To make it even more simpler:

Each number in set A can match exactly one number in set B to equal 9.

So if you choose any number from set A, the probability that you choose the right number from set B is 1/5, because only one number out of the 5 will be the right match to equal 9. Therefore the answer is .20.
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hi

by Jeff@TargetTestPrep » Mon Apr 09, 2018 3:37 pm
gmatpup wrote:A = {2, 3, 4, 5}

B= {4, 5, 6, 7, 8}

Two integers will be randomly selected from the sets above, one integer from set A and one integer from set B. WHat is the probability that the sum of the two integers will equal 9?

A. 0.15
B. 0.20
C. 0.25
D. 0.30
E. 0.33
Let’s first determine the total number of outcomes. We have 4 numbers in set A, and 5 in set B, and since we are selecting 1 number from each set, the total number of outcomes is 4 x 5 = 20.

For our favorable outcomes, we need to determine the number of ways we can get a number from set A and a number from set B to sum to 9. We are selecting from the following two sets:

A = {2, 3, 4, 5}

B = {4, 5, 6, 7, 8}

We will denote the first number as from set A and the second from set B. Here are the pairings that yield a sum of 9:

2,7
3,6
4,5
5,4

We see that there are 4 favorable outcomes. Thus, the probability is 4/20 = 1/5 = 0.2.

Answer: B

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