Hi,
This question is from the Official Guide 12th edition.
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
The answer is B.
The explantion provided by OG is:
The total number of different pairs of numbers,
one from set A and one from set B is (4)(5) = 20.
Of these 20 pairs of numbers, there are 4 possible
pairs that sum to 9: 2 and 7, 3 and 6, 4 and 5, and
5 and 4. Thus, the probability that the sum of the
two integers will be 9 is equal to 4/20= 0.2
The correct answer is B.
As per my understanding I get 3 pairs :ie: 2 and 7, 3 and 6, 4 and 5.
I dont understand why the explanation takes into account 5 and 4. if the explanation says 5 and 4 is a pair then going by that fashion, 6 and 3, 7 and 2 should be two more pairs.
Can someone pls explain this to me.
Thanks
This question is from the Official Guide 12th edition.
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
The answer is B.
The explantion provided by OG is:
The total number of different pairs of numbers,
one from set A and one from set B is (4)(5) = 20.
Of these 20 pairs of numbers, there are 4 possible
pairs that sum to 9: 2 and 7, 3 and 6, 4 and 5, and
5 and 4. Thus, the probability that the sum of the
two integers will be 9 is equal to 4/20= 0.2
The correct answer is B.
As per my understanding I get 3 pairs :ie: 2 and 7, 3 and 6, 4 and 5.
I dont understand why the explanation takes into account 5 and 4. if the explanation says 5 and 4 is a pair then going by that fashion, 6 and 3, 7 and 2 should be two more pairs.
Can someone pls explain this to me.
Thanks
