Hi all,

I was just doing problems related to speed, distance, and time and came across a few where we need to either find the net rate or the combined rate. I don’t quite understand the concept of when we add the rates and when we subtract them. Greg mentioned in his videos that we need to identify whether two things contribute to the same goal. For example, in “catch up” problems we usually find the net rate, why is that so? How do we know what the “goal” is?

Can you provide an example question where are you getting stuck exactly ?

Also, you can read more theory and checkout some worked example in-herehttps://gmatclub.com/forum/work-rate-problems-all-in-one-topic-205201.html

In-case your doubt is about relative speed then: https://gmatclub.com/forum/time-speed-and-distance-simplified-150163.html

This is one example. In the solution, they found the net rate. I guess where I am getting confused is that when two objects are moving in the same direction why do we find the net rate? Aren’t they moving towards the same goal?

Thank you for sharing the additional resources I’ll take a look at them