Fraction/Ratio

BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

This topic has expert replies

Post new topic Post Reply

Previous Topic Next Topic

BTGmoderatorRO: Moderator; Posts: 772; Joined: Wed Aug 30, 2017 6:29 pm; Followed by:6 members

Fraction/Ratio

by BTGmoderatorRO » Fri Dec 29, 2017 5:12 am

Timer

00:00

Your Answer

Global Stats

The ratio of spinsters to cats is 2 to 7. If there are 25 more cats than spinsters, how many spinsters are there?

A. 10
B. 12
C. 15
D. 18
E. 27

OA is A

What is the best approach to solving this question?

Quote

Source: Beat The GMAT — Problem Solving | Fri Dec 29, 2017 5:12 am

EconomistGMATTutor: GMAT Instructor; Posts: 555; Joined: Wed Oct 04, 2017 4:18 pm; Thanked: 180 times; Followed by:12 members

Fraction/Ratio

by EconomistGMATTutor » Fri Dec 29, 2017 11:16 am

The ratio of spinsters to cats is 2 to 7. If there are 25 more cats than spinsters, how many spinsters are there?

A. 10
B. 12
C. 15
D. 18
E. 27

OA is A

What is the best approach to solving this question?

Hi Roland2rule,
Let's take a look at your question.

Let S denotes the spinsters and C denotes the cats, then
$$\frac{S}{C}=\frac{2}{7}$$
$$7S=2C ... (i)$$

If there are 25 more cats then spinsters, we can write it as,
$$C=S+25$$
Substitute C in eq(i), we get,
$$7S=2\left(S+25\right)$$
$$7S=2S+50$$
$$7S-2S=50$$
$$5S=50$$
$$S=\frac{50}{5}=10$$
When there are 25 more cats then spinsters, then there are 10 spinsters.

Therefore, Option A is correct.

Hope it helps.
I am available if you'd like any follow up.

GMAT Prep From The Economist
We offer 70+ point score improvement money back guarantee.
Our average student improves 98 points.

Quote

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 » Fri Dec 29, 2017 12:44 pm

Roland2rule wrote:The ratio of spinsters to cats is 2 to 7. If there are 25 more cats than spinsters, how many spinsters are there?

A. 10
B. 12
C. 15
D. 18
E. 27

Another option is to list equivalent ratios

GIVEN: The ratio of spinsters to cats is 2 to 7
So, it's possible that there are 2 spinsters and 7 cats [difference = 7 - 2 = 5.....we need a difference of 5]
It's also possible that there are 4 spinsters and 14 cats [difference = 14 - 4 = 10.....we need a difference of 5]
Or there are 6 spinsters and 21 cats [difference = 15.....we need a difference of 5]
Or there are 8 spinsters and 28 cats [difference = 20.....we need a difference of 5]
Or there are 10 spinsters and 35 cats [difference = 25.... BINGO!!!]

So, there are 10 spinsters
Answer: A

Cheers,
Brent

Brent Hanneson - Creator of GMATPrepNow.com

Quote

GMAT/MBA Expert

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 Aug 25, 2019 5:48 pm

BTGmoderatorRO wrote:The ratio of spinsters to cats is 2 to 7. If there are 25 more cats than spinsters, how many spinsters are there?

A. 10
B. 12
C. 15
D. 18
E. 27

OA is A

What is the best approach to solving this question?

We can re-express the ratio of spinsters to cats as 2x : 7x, where 2x = the number of spinsters and 7x = the number of cats. We can create the equation:

7x - 25 = 2x

5x = 25

x = 5

Thus, there are 2 * 5 = 10 spinsters.

Answer: A

Scott Woodbury-Stewart
Founder and CEO
[email protected]