Fractions/Ratios/Decimals, Number Properties

This topic has expert replies
Legendary Member
Posts: 2499
Joined: Sun Oct 29, 2017 2:04 pm
Followed by:6 members

Fractions/Ratios/Decimals, Number Properties

by swerve » Thu Apr 09, 2020 1:20 pm

Timer

00:00

Your Answer

A

B

C

D

E

Global Stats

Which of the following could be the sum of the reciprocals of two different prime numbers?

A. \(\dfrac{7}{13}\)
B. \(\dfrac{10}{12}\)
C. \(\dfrac{11}{30}\)
D. \(\dfrac{23}{50}\)
E. \(\dfrac{19}{77}\)

The OA is B

Source: GMAT Paper Tests
Source: — Problem Solving |

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16207
Joined: Mon Dec 08, 2008 6:26 pm
Location: Vancouver, BC
Thanked: 5254 times
Followed by:1268 members
GMAT Score:770
swerve wrote:
Thu Apr 09, 2020 1:20 pm
Which of the following could be the sum of the reciprocals of two different prime numbers?

A. \(\dfrac{7}{13}\)
B. \(\dfrac{10}{12}\)
C. \(\dfrac{11}{30}\)
D. \(\dfrac{23}{50}\)
E. \(\dfrac{19}{77}\)

The OA is B

Source: GMAT Paper Tests
Let p and q be the two prime numbers

So the sum of their reciprocals = 1/p + 1/q = q/pq + p/pq = (q + p)/pq
This means we are looking for an answer choice in which the numerator can be expressed as the SUM of two prime numbers, and the denominator can be expressed as the PRODUCT of those same two prime numbers.

Check the answer choices....

B) 10/12 = 5/6 = (2 + 3)/(2)(3) perfect!!!

Answer: B

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 8086
Joined: Sat Apr 25, 2015 10:56 am
Location: Los Angeles, CA
Thanked: 43 times
Followed by:29 members
swerve wrote:
Thu Apr 09, 2020 1:20 pm
Which of the following could be the sum of the reciprocals of two different prime numbers?

A. \(\dfrac{7}{13}\)
B. \(\dfrac{10}{12}\)
C. \(\dfrac{11}{30}\)
D. \(\dfrac{23}{50}\)
E. \(\dfrac{19}{77}\)

The OA is B

Source: GMAT Paper Tests
Since 1/2 + 1/3 = 3/6 + 2/6 = 5/6 = 10/12, the correct answer is B.

Answer: B

Scott Woodbury-Stewart
Founder and CEO
[email protected]

Image

See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews

ImageImage