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# A qualified worker digs a well in 5 hours. He invites 2

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Director
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A qualified worker digs a well in 5 hours. He invites 2 [#permalink]  14 Jun 2007, 10:34
A qualified worker digs a well in 5 hours. He invites 2 apprentices who work 3/4 as fast and
2 trainees who work 1/5 as fast as he does. If the five-person team digs the same well, how much time
does the team need to finish the job?

a.1.20
b.1.30
c.1.40
d.1.50
e.2.10
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[#permalink]  14 Jun 2007, 14:52
My choice is B: 1.30 approx...

What is the OA?
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[#permalink]  14 Jun 2007, 15:48
Q rate/day = 1/5
A=(3/4)(1/5)=(3/20)(2)=3/10
T=(1/5)(1/5)=(1/25)(2)=2/25

t(1/5+3/10+2/25)=1 = 29/50 --> t= 50/29 or 1:40
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[#permalink]  14 Jun 2007, 16:00
Right, it is C! made a mistake
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[#permalink]  14 Jun 2007, 22:12
Well done XY, I solved it exactly the same way. Tip for people looking for quicker ways / short cuts, as soon as you reach 50/29, if 50/29 is NOT one of the choices, approximate !!!
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[#permalink]  14 Jun 2007, 23:28
bsd_lover wrote:
Well done XY, I solved it exactly the same way. Tip for people looking for quicker ways / short cuts, as soon as you reach 50/29, if 50/29 is NOT one of the choices, approximate !!!

50/29 is appx 1.7...so..D..
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[#permalink]  15 Jun 2007, 10:57
Juaz, you'd be right if the hour had 100 minutes.

Since we know that it has 60 mins, 50/29 times 60 gives us a little over 100 min. 100 min is an hour and 40!

Ans is C!
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[#permalink]  01 Jul 2007, 11:57
I must be totally blind! I do not see how you can get 1.4 hours out of 50/29.

Here's how I see it: each hour 29/50 of the job is completed, therefore after the first hour, 29/50 is complete and 21/50 is still remaining to be completed. 21/50 is just slightly less than 29/50, which is inline with the 1.7 that Juaz got.

Can someone please explain what I am missing?

Thanks!
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[#permalink]  01 Jul 2007, 12:11
Bluebird wrote:
I must be totally blind! I do not see how you can get 1.4 hours out of 50/29.

Here's how I see it: each hour 29/50 of the job is completed, therefore after the first hour, 29/50 is complete and 21/50 is still remaining to be completed. 21/50 is just slightly less than 29/50, which is inline with the 1.7 that Juaz got.

Can someone please explain what I am missing?

Thanks!

50/29 = 1.7 hrs

(.7)60 = approx 40 mins

so total time = 1 hour and 40 mins.

I think the answers are a bit confusing.
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[#permalink]  01 Jul 2007, 12:19
Thank you salr15! I am quite embarrassed, but you're right, the answers are a bit confusing... 1.4 to me means 1.4 hours, not 1 hr and 40 minutes. Thank you for the clarification!
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[#permalink]  16 Oct 2007, 02:12
Well, technically --- the question asks:
"how much time does the team need to finish the job?"

After the work calculation, we are left with 50/29 hours. This is equivalent to 1 hour and 21/29*60 minutes.

21/29 roughly yields "0.7241" which multiplied by 60 is roughly equivalent to 43.4 minutes.

Therefore, if we give the team 1:40 minutes, they will NOT be able to complete the job. --- Amongst the available choices, the team NEEDS 1:50 minutes to complete the job.

Is my logic wrong on this?
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[#permalink]  16 Oct 2007, 02:13
Well, technically --- the question asks:
"how much time does the team need to finish the job?"

After the work calculation, we are left with 50/29 hours. This is equivalent to 1 hour and 21/29*60 minutes.

21/29 roughly yields "0.7241" which multiplied by 60 is roughly equivalent to 43.4 minutes.

Therefore, if we give the team 1:40 minutes, they will NOT be able to complete the job. --- Amongst the available choices, the team NEEDS 1:50 minutes to complete the job.

Is my logic wrong on this?
[#permalink] 16 Oct 2007, 02:13
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