The 4:00 Meeting
Tom and Bill are standing at two places on a straight road. Tom starts
walking toward Bill and arrives at Bill’s original place 11 minutes after
Bill had left. At perhaps a different time, Bill starts walking toward Tom
and arrives at Tom’s original place 15 minutes after Tom had left. When
each reaches the other’s original place, he immediately turns and starts
back, and they meet in the center at 4:00. Assuming that they walked at
constant rates, when did each start to travel on the road?
Alice Forgets Her Purse
On her way out of Macys, Alice walks down a down-moving escalator
in 50 steps. When she reaches the bottom, she suddenly remembers
she forgot her purse, and she turns and runs back up the escalator in
125 steps, stepping five times as fast as she went down. How many steps
are on the surface of the escalator?
The Twelve Coins
You have 12 coins. They are identical, except that one of them is either
heavier or lighter than the rest. In three weighings on a balance scale, find
the odd coin and whether it’s heavier or lighter.