Distance/Rate problem

[1a2s3d4f5g6h7j8k9l]

Hi all,

Dana drove from A to B at a rate of 40 miles per hour. At what speed should she return so that her average speed for the round trip will be 50 miles per hour?

Please help.....Thanks!

 

[tkhunny]

Total Distance = Total Rate * Total Time

How do the distances relate to each other, trip out vs. trip in?
How do the rates relate to each other?