If a certain concrete mixture contains gravel, water, and

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by AAPL » Wed Jan 16, 2019 5:45 am

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Princeton Review

If a certain concrete mixture contains gravel, water, and sand in a 1 to 3 to 5 ratio by weight, how many pounds of gravel would be needed to produce 72 pounds the mixture?

A. 72
B. 40
C. 24
D. 9
E. 8

OA E

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Source: Beat The GMAT — Problem Solving | Wed Jan 16, 2019 5:45 am

swerve: Legendary Member; Posts: 2535; Joined: Sun Oct 29, 2017 2:04 pmFollowed by: 6 members

by swerve » Wed Jan 16, 2019 10:21 am

We can solve this question as follows,

1X + 3X + 5X = 72
9X = 72
X=8.

Hence, E is the correct answer.

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by [email protected] » Wed Jan 16, 2019 10:42 am

Hi All,

We're told that a certain concrete mixture contains gravel, water, and sand in a ratio of 1 to 3 to 5 by weight. We're asked for the number of pounds of gravel that would be needed to produce 72 pounds of the mixture. This math behind this question can be approached in a number of different ways (depending on how you want to work through your calculations).

To start, a ratio of 1:3:5 means that for every 1 pound of gravel, we'll need 3 pounds of water and 5 pounds of sand. In essence, for every 1+3+5 = 9 pounds of this mixture, 1 pound of it will be gravel.

With 72 total pounds, we have 72/9 = 8 'sets' of the 1:3:5 mixture described), so we would have 8(1) = 8 pounds of gravel, 8(3) = 24 pounds of water and 8(5) = 40 pounds of sand. You'll notice that all 3 of those numbers are in the answer choices; we're asked for the number of pounds of GRAVEL though...

Final Answer: E

GMAT assassins aren't born, they're made,
Rich

Contact Rich at [email protected]

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Scott@TargetTestPrep: GMAT Instructor; Posts: 8134; Joined: Sat Apr 25, 2015 10:56 amFollowed by: 29 members; Location: Los Angeles, CA; Thanked: 43 times

by Scott@TargetTestPrep » Mon Jan 21, 2019 5:49 pm

AAPL wrote:Princeton Review

If a certain concrete mixture contains gravel, water, and sand in a 1 to 3 to 5 ratio by weight, how many pounds of gravel would be needed to produce 72 pounds the mixture?

A. 72
B. 40
C. 24
D. 9
E. 8

We can create the ratio:

Gravel : water : sand = x : 3x : 5x

We can create the equation:

x + 3x + 5x = 72

9x = 72

x = 8

So the number of pounds of gravel is 8.

Answer: E

Scott Woodbury-Stewart
Founder and CEO
[email protected]

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