1/3 +1/2 - 5/6 + 1/5 + 1/4 - 9/20 =

This topic has expert replies
Moderator
Posts: 2058
Joined: Sun Oct 29, 2017 4:24 am
Thanked: 1 times
Followed by:5 members

1/3 +1/2 - 5/6 + 1/5 + 1/4 - 9/20 =

by M7MBA » Sun Dec 10, 2017 10:56 am
1/3 +1/2 - 5/6 + 1/5 + 1/4 - 9/20 =

A. 0
B. 2/15
C. 2/5
D. 9/20
E. 5/6

The OA is A.

Experts, is there a fast way to solve this? There are many fractions.

User avatar
Legendary Member
Posts: 2663
Joined: Wed Jan 14, 2015 8:25 am
Location: Boston, MA
Thanked: 1153 times
Followed by:128 members
GMAT Score:770

by DavidG@VeritasPrep » Sun Dec 10, 2017 11:03 am
M7MBA wrote:1/3 +1/2 - 5/6 + 1/5 + 1/4 - 9/20 =

A. 0
B. 2/15
C. 2/5
D. 9/20
E. 5/6

The OA is A.

Experts, is there a fast way to solve this? There are many fractions.
Split it into two pieces, each of which allows for an easy calculation for your common denominator
Piece One: 1/3 + 1/2 - 5/6
3/6 + 2/6 - 5/6 = 5/6 - 5/6 = 0

Piece Two: 1/5 + 1/4 - 9/20
4/20 + 5/20 - 9/20 = 9/20 - 9/20 = 0

0 + 0 = 0. The answer is A
Veritas Prep | GMAT Instructor

Veritas Prep Reviews
Save $100 off any live Veritas Prep GMAT Course

User avatar
GMAT Instructor
Posts: 15539
Joined: Tue May 25, 2010 12:04 pm
Location: New York, NY
Thanked: 13060 times
Followed by:1906 members
GMAT Score:790

by GMATGuruNY » Mon Dec 11, 2017 3:56 am
M7MBA wrote:1/3 +1/2 - 5/6 + 1/5 + 1/4 - 9/20 =

A. 0
B. 2/15
C. 2/5
D. 9/20
E. 5/6
Set the equation equal to x and multiply by the LCM of the denominators (60):

x = 1/3 +1/2 - 5/6 + 1/5 + 1/4 - 9/20

60x = 60(1/3 +1/2 - 5/6 + 1/5 + 1/4 - 9/20)

60x = 20 + 30 - 50 + 12 + 15 - 27

60x = 50 - 50 + 27 - 27

60x = 0

x = 0.

The correct answer is A.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.

As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.

For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3

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

by Brent@GMATPrepNow » Mon Dec 11, 2017 8:02 am
M7MBA wrote:1/3 +1/2 - 5/6 + 1/5 + 1/4 - 9/20 =

A. 0
B. 2/15
C. 2/5
D. 9/20
E. 5/6
For integers x and y, we can say: 1/x + 1/y = (x + y)/xy

Applying this property, we get:
1/3 +1/2 - 5/6 + 1/5 + 1/4 - 9/20 = (3 + 2)/(3)(2) - 5/6 + (5 + 4)/(5)(4)- 9/20
= 5/6 - 5/6 + 9/20 - 9/20
= 0
= A

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