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

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Danny and Ian are munching on a jar full of candies. Had Dan [#permalink] New post 19 Dec 2012, 23:40
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Question Stats:

31% (02:08) correct 68% (00:47) wrong based on 3 sessions
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

Source: HULT
[Reveal] Spoiler: OA

Last edited by Bunuel on 20 Dec 2012, 02:32, edited 1 time in total.
Edited the question.
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Re: Danny and Ian are munching on a jar full of candies. [#permalink] New post 19 Dec 2012, 23:42
I thought it should be inverse of the combined rates which is (10*5)/(10+5)=50/15=3+ minutes right? OA says a different one.... what am I doing wrong?
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Re: Danny and Ian are munching on a jar full of candies. [#permalink] New post 19 Dec 2012, 23:52
Amateur wrote:
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?

2.5 minutes

3 minutes

3 minutes and 20 seconds

6 minutes and 40 seconds

4 minutes

Source: HULT


Hi,

Danny's does in 5 minutes
Ian finishes half in 10 minutes i.e finishes the jar in 20 minutes

Therefore Combined rate will be

1/5+1/20=1/T

5/20= 1/T ==> T = 4 min
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Re: Danny and Ian are munching on a jar full of candies. [#permalink] New post 20 Dec 2012, 02:36
Amateur wrote:
I thought it should be inverse of the combined rates which is (10*5)/(10+5)=50/15=3+ minutes right? OA says a different one.... what am I doing wrong?


We are told that Ian needs 10 minutes to finish HALF the jar, so he needs 20 minute to finish full jar.

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 rate of Danny is 1/5 jar/minute and the rate of Ian is 1/20 jar/minute, their combined rate is 1/5+1/20=1/4 jar/minute. Thus together they need 4 minutes to finish the jar.

Answer: E.
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Re: Danny and Ian are munching on a jar full of candies.   [#permalink] 20 Dec 2012, 02:36
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