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?

Owen can read a 100 page book, which had 500 words per page. It took him 2 hours less time than it takes him to read a 150 page book with 600 words per page. How long would it take him to read a 400 page book which had 400 words per page?

If Jameson can build a 20 foot wall in 6 hours, and Jaqueline can build a 50 foot wall in 12 hours, and the two of them work together to build a 180 foot wall (with each of them starting at opposite ends of the wall), how much wall will each build before the wall is complete?

A clock adjusts its timing each night by contacting a satellite at 2:00 AM to find out the official standard time. Since it has a mechanical action with physical minute, second and hour hands, if the clock finds out it is out of sync, it will move at 12 times normal speed in order to "catch up" with the actual time. (If it is ahead of the correct time, it will still move forward, until it wraps around to the correct time.)

In the fall, when Daylight Savings Time happens, at 2:00 the satellite tells the clock that it is actually 1:00. Thus, the clock has to move forward at high speed until it wraps around to the correct time.

How long will it take the clock to be displaying the correct time again?