There are three different hoses used to fill a pool: hose x,

Expert replies

Previous Topic Next Topic

BTGmoderatorLU: Moderator; Posts: 2598; Joined: Sun Oct 15, 2017 1:50 pmFollowed by: 6 members

by BTGmoderatorLU » Thu Sep 06, 2018 6:53 pm

Timer

00:00

Answers

Stats

Difficulty—

Source: Veritas Prep

There are three different hoses used to fill a pool: hose x, hose y, and hose z. Hose x can fill the pool in a days, hose y in b days, and hose z in c days, where a > b > c. When all three hoses are used together to fill a pool, it takes d days to fill the pool. Which of the following must be true?
I. d<c
II. d>b
III. c/3<d<a/3

A. I only
B. III only
C. I and III only
D. II only
E. I, II and III

The OA is C.

Like this post

Source: Beat The GMAT — Problem Solving | Thu Sep 06, 2018 6:53 pm

GMAT/MBA Expert

Jay@ManhattanReview: GMAT Instructor; Posts: 3008; Joined: Mon Aug 22, 2016 6:19 amFollowed by: 34 members; Location: Grand Central / New York; Thanked: 470 times

by Jay@ManhattanReview » Thu Sep 06, 2018 9:41 pm

BTGmoderatorLU wrote:Source: Veritas Prep

There are three different hoses used to fill a pool: hose x, hose y, and hose z. Hose x can fill the pool in a days, hose y in b days, and hose z in c days, where a > b > c. When all three hoses are used together to fill a pool, it takes d days to fill the pool. Which of the following must be true?

I. d < c
II. d > b
III. c/3 < d < a/3

A. I only
B. III only
C. I and III only
D. II only
E. I, II and III

The OA is C.

Like this post

GMAT/MBA Expert

Jay@ManhattanReview: GMAT Instructor; Posts: 3008; Joined: Mon Aug 22, 2016 6:19 amFollowed by: 34 members; Location: Grand Central / New York; Thanked: 470 times

by Jay@ManhattanReview » Thu Sep 06, 2018 9:48 pm

BTGmoderatorLU wrote:Source: Veritas Prep

There are three different hoses used to fill a pool: hose x, hose y, and hose z. Hose x can fill the pool in a days, hose y in b days, and hose z in c days, where a > b > c. When all three hoses are used together to fill a pool, it takes d days to fill the pool. Which of the following must be true?

I. d < c
II. d > b
III. c/3 < d < a/3

A. I only
B. III only
C. I and III only
D. II only
E. I, II and III

The OA is C.

If there were only z hose in operation, the pool would fill in c days; however, since two more hoses are helping hose z, the pool would fill in less than c days; thus, d < c. Statement I is correct.

Also, since b > c and d < c, we have d < b; thus, Statement II is incorrect.

Assuming that a, b and c are nearly equal to each other, thus, the pool would fill in c/3 days, or d = c/3; however, it is not so since a > b > c, thus, a/3 > d > c/3. So, statement III is also correct.

The correct answer: C

Hope this helps!

-Jay
_________________
Manhattan Review GRE Prep

Locations: GMAT Classes Boston | GRE Prep Course NYC | GRE Prep Dallas | SAT Prep Classes Houston | and many more...

Schedule your free consultation with an experienced GMAT Prep Advisor! Click here.

Like this post

GMAT/MBA Expert

Scott@TargetTestPrep: GMAT Instructor; Posts: 8199; Joined: Sat Apr 25, 2015 10:56 amFollowed by: 29 members; Location: Los Angeles, CA; Thanked: 43 times

by Scott@TargetTestPrep » Mon Sep 17, 2018 5:36 pm

There are three different hoses used to fill a pool: hose x, hose y, and hose z. Hose x can fill the pool in a days, hose y in b days, and hose z in c days, where a > b > c. When all three hoses are used together to fill a pool, it takes d days to fill the pool. Which of the following must be true?

I. d < c
II. d > b
III. c/3 < d < a/3

A. I only
B. III only
C. I and III only
D. II only
E. I, II and III

Roman numeral I is true. When all three hoses work together, the number of days it takes must be less than the number of days it takes for any individual hose to complete the job by itself. Using the same argument, we see that Roman numeral II can't be true.

If each hose works as fast as hose z, it will take exactly c/3 days. However, since they do not, and since hose z is the fastest, they must take more than c/3 days. That is, d > c/3. Similarly, if each hose works as fast as hose x, it will take exactly a/3 days. However, since they do not, and since hose x is the slowest, they must take less than a/3 days. That is, d < a/3. We see that c/3 < d < a/3, which means Roman numeral III is true also.

Answer: C

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