John drove at 20 mph for 30 minutes, and then he drove back home at 10 mph. What was his average speed for the entire trip?

I have four books, each with n pages, and I can read them all in four hours.

I have four more books, each with each 120 fewer pages than my original four books. I can read them all in three hours.

I have five more books, each with 120 more pages than my original four books. How long would it take me to read all five books?

Jack can mow a lawn in 6 hours, and Jane can mow it in 4 hours. If they work together, how long will it take them to mow the lawn? Give your answer in minutes.

A car can travel from city A to city B in 8 hours. If its speed during the return journey was decreased by 7 mph, it would take 9 hours to get back to city A. How far apart are the two cities?

Geoge the Monkey can run at a speed of 12 mph. Hazel can walk at a rate of 4 mph, and Henrietta can walk at a rate of 2 mph.

George is standing halfway between Hazel and Henrietta, who are 1,320 feet apart, and begin walking toward each other.

At the moment they begin walking, George begins running toward Hazel. When he reaches her, he turns around and runs to Henrietta. Upon reaching her, he turns around again, and continues on like this, until the two girls meet, and he is sandwiched between them.

How far did George run?

Marco walks a certain distance at a certain speed (measured in miles per hour), and then returns over the same distance at a speed one mph less than his original walking speed. He took a total of 35 hours. If, instead of slowing down for his return journey, he had sped up by one mph, his journey would have taken 27 hours. How far did he walk?