In a town of 8,000 residents, 65 percent of all residents ow

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ktrout2020: Senior | Next Rank: 100 Posts; Posts: 41; Joined: Wed Oct 30, 2019 1:10 pm

In a town of 8,000 residents, 65 percent of all residents ow

by ktrout2020 » Thu Oct 31, 2019 6:17 am

In a town of 8,000 residents, 65 percent of all residents own a car, 55 percent own a motorcycle, and 25 percent own neither a car nor a motorcycle. How many residents own a car but not a motorcycle?

A. 800
B. 1,600
C. 2,000
D. 3,600
E. 4,400

Source: Manhattan Prep
Answer: B

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Source: Beat The GMAT — Problem Solving | Thu Oct 31, 2019 6:17 am

GMAT/MBA Expert

Brent@GMATPrepNow: 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 » Sat Nov 02, 2019 5:05 am

ktrout2020 wrote:In a town of 8,000 residents, 65 percent of all residents own a car, 55 percent own a motorcycle, and 25 percent own neither a car nor a motorcycle. How many residents own a car but not a motorcycle?

A. 800
B. 1,600
C. 2,000
D. 3,600
E. 4,400

Source: Manhattan Prep
Answer: B

One approach is to use the Double Matrix Method.
This technique can be used for most questions featuring a population in which each member has two characteristics associated with it (aka overlapping sets questions).
Here, we have a population of residents, and the two characteristics are:
- own a car or do not own a car
- own a motorcycle or do not own a motorcycle

65% of 8000 = 5200
55% of 8000 = 4400
25% of 8000 = 2000

So, our matrix looks like this so far:

Since there are 8000 resident altogether, we know that, if 5200 own a car, then 2800 do NOT own a car
And, if 4400 own a motorcycle, then 3600 do NOT own a motorcycle
We get:

When we fill in the rest of the matrix we get:

Brent Hanneson - Creator of GMATPrepNow.com

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Scott@TargetTestPrep: GMAT Instructor; Posts: 8086; Joined: Sat Apr 25, 2015 10:56 am; Location: Los Angeles, CA; Thanked: 43 times; Followed by:29 members

by Scott@TargetTestPrep » Sun Nov 03, 2019 7:33 pm

ktrout2020 wrote:In a town of 8,000 residents, 65 percent of all residents own a car, 55 percent own a motorcycle, and 25 percent own neither a car nor a motorcycle. How many residents own a car but not a motorcycle?

A. 800
B. 1,600
C. 2,000
D. 3,600
E. 4,400

Source: Manhattan Prep
Answer: B

Let's start with making the total 100 percent; thus:

Total = Car owners + Motorcycle owners - both + neither

100 = 65 + 55 - both + 25

100 = 145 - both

Both = 45

So 65 - 45 = 20 percent of the 8,000 residents own a car but not a motorcycle, and 20% of 8,000 is 0.2 x 8,000 = 1,600.

Answer: B

Scott Woodbury-Stewart
Founder and CEO
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