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Hello, I'm having trouble working with this problem:
A capentry work can be done in 3 days by 12 persons. If 9 persons work on the same task, how long would it take them to finish it?
The correct answer is 4, but I don't understand how to get it.
I thought I had to do: 9 x 3 / 12, but it's not correct.
How can I solve this?
Thanks
12 persons work 3 days.Quote:
Originally Posted by norifurippu
then
1 person works 3 * 12 days
then
9 persons workdays.
12 persons do work in 3 days
So
Work done in 3days =1
Hence work done in 1day by 12 persons = 1/3
This is work done by 12 pewrsons
So the work done by 4 persons = 9/(3x12) = 3/12
thus to do complete work
Time taken =12/3= 4 days
Assuming every one works at the same rate, the each is working at a rate of (1/12) job in 3 days or 1/36 job per day. 9 people will work at 9/36= 1/4 job per day and so 4/1= 4 day per job: 4 days to do the job.Quote:
Originally Posted by norifurippu
By the way: your answer, 9 x 3/12= 27/12 is slightly larger than 2 days and so less than 3 days. You are saying that 9 people can do the job faster than 12 people! That should hae told you that you should have divided where you
multiplied.
How many man-days are consumed by twelve people working three days each? (Hint: Multiply.)Quote:
Originally Posted by norifurippu
If you divide that number of man-days between nine people, how many days would that require? (Hint: Divide.)
Have fun! :D
Thank you very much everyone! at first it appeared like a very easy problem, but it ended up requiring quite an amout of thinking, thanks!