Rate problems -- scenarios

[ammarjavaid007]

Hello,

This is just for my general understanding

On the SG, we learn about to types of rate problems: RTD and RTW.

Generally in RTD problems we need to add the times to find average rate and in RTW we add rates if 2 or more workers are working together.

I can't seem to remember but would there ever be a case where we add rates in an RTD (distance) question (apart from relative rate problems)?

OR

Add times in a rate problem? Can you give me a scenario please.

Thank you.

[RonPurewal]

It's always a bad idea to try to memorize anything that's context-dependent.
In other words, you shouldn't be trying to remember ANY "rules" for this kind of stuff. Just think about the context in whatever situation you're thinking about.

For instance, if two peole are walking toward each other at constant rates, then they're covering ground together"”so you can add the rates. And so on.

So, basically ... if the context dictates that you should add rates, then you should add rates.
E.g., let's say I'm on a train that's moving at 30 miles per hour, and I'm running at 10 miles per hour toward the front of the train. Then, relative to the ground, I'm moving at 40 miles per hour.

[RonPurewal]

Add times in a rate problem? Can you give me a scenario please.

Thank you.

Basically, you'd add times if the total time is somehow relevant. For instance:

* If you do something at the same rate for 2 different increments of time, then you can just add the times together... because you're doing whatever thing at the same rate both times.

* If you need to find average rate, that's defined as (total output)/(total time).
So, to find an average rate, you'd want to add up ALL the time, since that's the definition.

Etc.

Your life will be a lot easier if you don't try to create a bunch of unnecessary "categories" of situations. Just think about each situation as you encounter it.
(When you see the different situations in the strategy guide, you should just view them as illustrations of the different kinds of situations that are possible. You definitely shouldn't try to memorize them.)