A cleaning company mixed 4 cups (quick approach)

Question

A cleaning company mixed 4 cups of bleach with 7 cups of water to create a cleaning solution on Monday. On Tuesday, the cleaning company mixed 11 cups of bleach with 14 cups of water to create a cleaning solution. By approximately what percent did the ratio of bleach to water in the company's cleaning solution increase from Monday to Tuesday?

9%
12%
38%
50%
72%

Please recommend a quick solution (apart from the change / original * 100).

I am trying to work the problem as 4/7 = .56 and 11/14 ~ .70. But i am getting 25% as answer (which is not even an option).

Thanks for your help!

ganeshrkamath · Answer

melguy wrote:A cleaning company mixed 4 cups of bleach with 7 cups of water to create a cleaning solution on Monday. On Tuesday, the cleaning company mixed 11 cups of bleach with 14 cups of water to create a cleaning solution. By approximately what percent did the ratio of bleach to water in the company's cleaning solution increase from Monday to Tuesday?

9%
12%
38%
50%
72%

Please recommend a quick solution (apart from the change / original * 100).

I am trying to work the problem as 4/7 = .56 and 11/14 ~ .70. But i am getting 25% as answer (which is not even an option).

Thanks for your help!

B/W on Monday = 4/7 = 8/14
B/W on Tuesday = 11/14

Percentage increase = (11/14 - 8/14) / (8/14) * 100%
= 3/8 * 100%
= 37.5%

Choose C

Cheers

Every job is a self-portrait of the person who did it. Autograph your work with excellence.

Kelley School of Business (Class of 2016)
GMAT Score: 750 V40 Q51 AWA 5 IR 8
https://www.beatthegmat.com/first-attemp ... tml#688494

ganeshrkamath · Answer

melguy wrote:Please recommend a quick solution (apart from the change / original * 100).

I am trying to work the problem as 4/7 = .56 and 11/14 ~ .70. But i am getting 25% as answer (which is not even an option).

Thanks for your help!

One tip:
Try to work with fractions as far as possible. Most problems in GMAT are meant to be solved in fractions.
Converting fractions to decimals wastes valuable time and potentially results in wrong answers.

All the best.

Every job is a self-portrait of the person who did it. Autograph your work with excellence.

Kelley School of Business (Class of 2016)
GMAT Score: 750 V40 Q51 AWA 5 IR 8
https://www.beatthegmat.com/first-attemp ... tml#688494

melguy · Answer

ganeshrkamath wrote: B/W on Monday = 4/7 = 8/14
B/W on Tuesday = 11/14

Percentage increase = (11/14 - 8/14) / (8/14) * 100%
= 3/8 * 100%
= 37.5%

Cheers

I used this method earlier too but exam pressure does funny things to me...I made a mistake along the way! Thanks for your help!

GMATGuruNY · Answer

melguy wrote:A cleaning company mixed 4 cups of bleach with 7 cups of water to create a cleaning solution on Monday. On Tuesday, the cleaning company mixed 11 cups of bleach with 14 cups of water to create a cleaning solution. By approximately what percent did the ratio of bleach to water in the company's cleaning solution increase from Monday to Tuesday?

9%
12%
38%
50%
72%

Please recommend a quick solution (apart from the change / original * 100).

I am trying to work the problem as 4/7 = .56 and 11/14 ~ .70. But i am getting 25% as answer (which is not even an option).

Thanks for your help!

B/W on Monday = 4/7 = 8/14
B/W on Tuesday = 11/14

Percentage increase = (11/14 - 8/14) / (8/14) * 100%
= 3/8 * 100%
= 37.5%

Choose C

Cheers

Every job is a self-portrait of the person who did it. Autograph your work with excellence.

Kelley School of Business (Class of 2016)
GMAT Score: 750 V40 Q51 AWA 5 IR 8
https://www.beatthegmat.com/first-attemp ... tml#688494

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