Fraction/Ratio

Expert replies

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

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

Like this post

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 pmFollowed by: 12 members; Thanked: 180 times

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.

Like this post

GMAT/MBA Expert

Brent@GMATPrepNow: GMAT Instructor; Posts: 16207; Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members; Location: Vancouver, BC; Thanked: 5254 times; 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

Like this post

GMAT/MBA Expert

Scott@TargetTestPrep: GMAT Instructor; Posts: 8156; Joined: Sat Apr 25, 2015 10:56 amFollowed by: 29 members; Location: Los Angeles, CA; Thanked: 43 times

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]

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

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

560 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (560 Reviews)

"Target Test Prep is the closest to the official version of the GMAT exam, about 99% accuracy in terms of the quality and quantity of information. The course has excellently created singular sets of focused lessons and tests for every possible topic that one could come across in the official GMAT exam."

"The TTP course maximizes the efficiency of the time you spend studying. It will take time and effort but I could almost guarantee that if you complete the course exactly as it is laid out you will get an amazing score. They also have a very responsive team willing to help with any questions you might have."

"TTP has two things that I think no other test prep company offers: A teaching approach that reinforces understanding and an attitude that will give you the mental preparedness needed to succeed on the test. TTP gives you a deep understanding of the concept you need to know while teaching you how to think."

Write a Review