Fredrik I.

asked • 09/13/14

Problemsolving

A group of 30 people works with a project, they are supposed to do the work in 60 days. When the group has been working for 10 days, the company tells them to hurry up, since they need to finish their work 20 days earlier than said before. With how many persons must the group be increased to make it in time?

1 Expert Answer

By:

Phillip R. answered • 09/13/14

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Fredrik I.

In the last part: X/30 = 2/3
Where did you get 2/3?
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09/13/14

Phillip R.

For the final 30 days of the project, the original 30 people will do 3/6th's. The fraction of the work still to be done is 2/6th's. The ratio 2/3 comes from the ratio 2/6 to 3/6 which is 2/3. So if 30 people do 3 parts (each part being 1/6), then x people do 2 parts. You can do x/30 = 2/3 or you can do 30/3 = x/2. Both proportions are equivalent. If you want to break it down in a formal way, you would say it takes 180people-days to do the job. Because only 5/6th's of the job remains after the first 10 days, we need another 150 people-days (180 x 5/6). We have 30 days, therefore we need 50 people to get 150 people-days. We already have 30 people so we need 20 more which is the same answer. 
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09/13/14

Phillip R.

Sorry it should be 1800 people-days (30 people x 60 days) and then 1500 people days left. Divide by 30 days to get 50 people. 
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09/13/14

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