Magoosh
A: {71,73,79,83,87}
B:{57,59,61,67}
If one number is selected at random from set A, and one number is selected at random from set B, what is the probability that both numbers are prime?
$$A.\ \frac{9}{20}$$
$$B.\ \frac{3}{5}$$
$$C.\ \frac{3}{4}$$
$$D.\ \frac{4}{5}$$
$$E.\ 1$$
OA B
If one number is selected at random from set A, and one
This topic has expert replies
GMAT/MBA Expert
- Jay@ManhattanReview
- GMAT Instructor
- Posts: 3008
- Joined: Mon Aug 22, 2016 6:19 am
- Location: Grand Central / New York
- Thanked: 470 times
- Followed by:34 members
Number of elements in Set A: {71, 73, 79, 83, 87} = 5; Number of primes in Set A = 4 (71, 73, 79, 83)AAPL wrote:Magoosh
A: {71,73,79,83,87}
B:{57,59,61,67}
If one number is selected at random from set A, and one number is selected at random from set B, what is the probability that both numbers are prime?
$$A.\ \frac{9}{20}$$
$$B.\ \frac{3}{5}$$
$$C.\ \frac{3}{4}$$
$$D.\ \frac{4}{5}$$
$$E.\ 1$$
OA B
Thus, the probability of choosing a prime number from Set A = 4/5
Number of elements in Set B: B:{57, 59, 61, 67} = 4; Number of primes in Set B = 3 (53, 61, 67)
Thus, the probability of choosing a prime number from Set B = 3/4
The probability that both numbers are prime = 4/5 * 3/4 = 3/5.
The correct answer: B
Hope this helps!
-Jay
_________________
Manhattan Review GMAT Prep
Locations: New Haven | Doha | Stockholm | Pretoria | and many more...
Schedule your free consultation with an experienced GMAT Prep Advisor! Click here.
GMAT/MBA Expert
- Scott@TargetTestPrep
- GMAT Instructor
- Posts: 7247
- Joined: Sat Apr 25, 2015 10:56 am
- Location: Los Angeles, CA
- Thanked: 43 times
- Followed by:29 members
There are 4 prime numbers in set A (71, 73, 79, 83) and 3 prime numbers in set B (59, 61, 67).AAPL wrote:Magoosh
A: {71,73,79,83,87}
B:{57,59,61,67}
If one number is selected at random from set A, and one number is selected at random from set B, what is the probability that both numbers are prime?
$$A.\ \frac{9}{20}$$
$$B.\ \frac{3}{5}$$
$$C.\ \frac{3}{4}$$
$$D.\ \frac{4}{5}$$
$$E.\ 1$$
OA B
Thus, the probability of selecting a prime in both sets is 4/5 x 3/4 = 3/5.
Answer: B
Scott Woodbury-Stewart
Founder and CEO
[email protected]
See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews