# Thread: Inverse Proportion. explanation needed

1. ## Inverse Proportion. explanation needed

Hi im studying for an exam and i have lost my sheet explaining how to do inverse proportion.

I have the question: A farmer has enough grain to feed 50 cattle for 10 days. He sells 10 cattle. For how many days will the grain last now?

The first time i went through i got the answer 12.5 days and i now do not know how to get back to that answer.

2. Originally Posted by Boredom
Hi im studying for an exam and i have lost my sheet explaining how to do inverse proportion.

I have the question: A farmer has enough grain to feed 50 cattle for 10 days. He sells 10 cattle. For how many days will the grain last now?

The first time i went through i got the answer 12.5 days and i now do not know how to get back to that answer.

There are (10)(50) = 500 units of grain.

500/40 = 12.5 => 12.5 days.

3. Hmm so simple.

Thanks

4. Originally Posted by Boredom
Hi im studying for an exam and i have lost my sheet explaining how to do inverse proportion.

I have the question: A farmer has enough grain to feed 50 cattle for 10 days. He sells 10 cattle. For how many days will the grain last now?

The first time i went through i got the answer 12.5 days and i now do not know how to get back to that answer.

Alternatively, it will take 50 cattle 10 days to eat the grain.
Imagine they all munch away at the same rate, even after the 10 were sold.

Take an intermediate step...
It will take one of them 50 times as long to eat all the grain, that's 500 days.
How long will it take 40 of them ?