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## In a particular state, 70 percent of the counties. . .

This topic has 1 expert reply and 0 member replies

### Top Member

Vincen Master | Next Rank: 500 Posts
Joined
07 Sep 2017
Posted:
458 messages
6

#### In a particular state, 70 percent of the counties. . .

Fri Sep 22, 2017 9:53 am
In a particular state, 70 percent of the counties received some rain on Monday, and 65 percent of the counties received some rain on Tuesday. No rain fell either day in 25 percent of the counties in the state. What percent of the counties received some rain on Monday and Tuesday?

(A) 12.5%
(B) 40%
(C) 50%
(D) 60%
(E) 67.5%

The OA is D.

This PS question with percentages confuse me. I need some help. Thanks.

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### GMAT/MBA Expert

Rich.C@EMPOWERgmat.com Elite Legendary Member
Joined
23 Jun 2013
Posted:
8949 messages
Followed by:
468 members
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GMAT Score:
800
Sat Sep 23, 2017 10:12 am
Hi Vincen,

This question is an example of a standard Overlapping Sets question. There are a couple of different ways that you can solve it, including the Overlapping Sets formula and the Tic-Tac-Toe Board/matrix grid. Here's how you can use the formula:

Total = (Group 1) + (Group 2) - (Both) + (Neither)

In this prompt, Group 1 is the counties that received rain on Monday and Group 2 is the counties that received rain on Tuesday.

100% = (70%) + (65%) - (Both) + (25%)
100% = 160% - Both
Both = 60%

GMAT assassins aren't born, they're made,
Rich

_________________
Contact Rich at Rich.C@empowergmat.com

Thanked by: Vincen

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