How do we know this is an inverse relationship? What do we need to look out for to determine if a relationship is direct or inverse?

What do you mean by “inverse relationship”?

This would be solved with work-rate formula right?

The fewer machines you have, the more time it would take to complete the task.

Oh I see!

I don’t have the exact source but in one of the videos Greg talks about Inverse relationships. For e.g. there is enough food on an island for 4 people to survive for 4 days then 1 person can survive how many days? This would be an inverse relationship and my question is , is this something we would have to think about for the above question?

Yes.