Danny and Ian are munching on a jar full of candies. Had

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AAPL: Moderator; Posts: 2632; Joined: Sun Oct 29, 2017 2:08 pmFollowed by: 2 members

by AAPL » Fri Jan 18, 2019 8:26 am

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Economist GMAT

Danny and Ian are munching on a jar full of candies. Had Danny eaten alone it would have taken him 5 minutes to finish the candies in the jar. Had Ian eaten alone it would have taken him 10 minutes to finish half the jar. Since both of them are eating simultaneously, how long would it take them to empty the jar?

A. 2.5 minutes
B. 3 minutes
C. 3 minutes and 20 seconds
D. 6 minutes and 40 seconds
E. 4 minutes

The OA is E

Source: Beat The GMAT — Problem Solving | Fri Jan 18, 2019 8:26 am

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by [email protected] » Fri Jan 18, 2019 10:35 am

Hi All,

This question is essentially a "Work Formula" question, since it has 2 people working on a task together. You have to be really careful with the details though, since the two given rates are NOT for the same task....

We're told that Danny can finish off the jar of candies in 5 minutes
We're told that Ian can finish off HALF the jar of candies in 10 minutes, which means that he can finish the WHOLE jar in 20 minutes.

We're asked how long it would take the two of them to finish the jar of candies together....

Work = (A)(B)/(A+B) where A and B are the individual rates of the two entities.

A = 5
B = 20

(5)(20)/(5+20) = 100/25 = 4 minutes to finish off the jar of candies.

Final Answer: E

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

Contact Rich at [email protected]

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by Scott@TargetTestPrep » Sun Jan 27, 2019 6:23 pm

AAPL wrote:Economist GMAT

Danny and Ian are munching on a jar full of candies. Had Danny eaten alone it would have taken him 5 minutes to finish the candies in the jar. Had Ian eaten alone it would have taken him 10 minutes to finish half the jar. Since both of them are eating simultaneously, how long would it take them to empty the jar?

A. 2.5 minutes
B. 3 minutes
C. 3 minutes and 20 seconds
D. 6 minutes and 40 seconds
E. 4 minutes

Danny's rate is 1/5, and Ian's rate is (1/2)/10. Thus, their combined rate is:

1/5 + (1/2)/10 = 1/5 + 1/20 = 4/20 + 1/20 = 5/20 = 1/4

So it would take them 1/(1/4) = 4 minutes to eat the whole jar of candies together.

Answer: E

Scott Woodbury-Stewart
Founder and CEO
[email protected]

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