Here is a problem to try and solve:

Jack and Jill walked along a level road, up the hill, back (along the same path) down te hill, and back along the same level road to home. They started out at 3pm and arrived home at 9pm. Their speed was four miles an hour on the level, three miles an hour uphill, and six miles an hour down hill.

a.) How far did they walk in all (level, up, down, level)?

b.) You can't figure out from the given information exactly when they reached the top of the hill. How closely can you approximate when they arrived there? (e.g. can you give an interval of an hour containing the time they arrived at the top? An interval of a half hour?)