# Math Help - Inverse proportion/Direct proportion question

1. ## Inverse proportion/Direct proportion question

Question: If 3 workers are required to build a 10m drain in 5 days, how many days will it take for 5 workers to build a 30m drain?

My first step is to calculate the inverse proportion of workers and days then I am stuck with the length of the drain. How do I go around to solve it?

2. ## Re: Inverse proportion/Direct proportion question

Originally Posted by FailInMaths
Question: If 3 workers are required to build a 10m drain in 5 days, how many days will it take for 5 workers to build a 30m drain?

My first step is to calculate the inverse proportion of workers and days then I am stuck with the length of the drain. How do I go around to solve it?
3 "identical" workers take 5 days to build 10 metres.
1 worker, working alone takes 3 times as long, that's 15 days for 10 metres,
which is 45 days for 30 metres.

5 workers take a fifth of the time.

3. ## Re: Inverse proportion/Direct proportion question

3 "identical" workers take 5 days to build 10 metres.
1 worker, working alone takes 3 times as long, that's 15 days for 10 metres,
which is 45 days for 30 metres.

5 workers take a fifth of the time.
Oh, I get it now, I thought it required complex stuff for the solution, stupid me

Thanks =)

4. ## Re: Inverse proportion/Direct proportion question

You could formulate the problem also, using the concept of "man days".

It takes 5(3) "man days" to build 10 metres

so it takes 5(3)(3) = 5(9) "man days" to build 3(10) = 30 metres.

That shows straight off how many days are required for 5 men.