Phillip R. answered • 09/13/14
Tutor
New to Wyzant
Top Notch Math and Science Tutoring from Brown Univ Grad
in ten days the group completed 1/6th of the project.
the current group of 30 people can complete another 3/6th of the project in the next 30 days, bringing them to the 40 days allotted to the project.
So the 30 people will do 4/6th of the project.
If you add X people to work during the additional 30 days to do 2/6th of the total project, then you can find X in your head or set up a proportion.
X/30 = 2/3
x = 20 people
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.
Report
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.
Report
09/13/14
Fredrik I.
Where did you get 2/3?
09/13/14