Riddles

בס"ד

After hearing many riddles last year, as one of the parents in my preschool room would come to share them, I have decided to pass them on. The girls in my school are having fun guessing and trying out them during the breaks. Here are some recent ones:

1. You have two threads of wool, unevenly spun. Each is made with enough wool to burn (as a wick) for one hour. However, it is impossible to tell at which point is halfway through the burning time on the string. With only these threads and a source of fire, can you measure exactly one and a half hours?

2. You have ten sacks - nine filled with real gold coins and one filled with false gold coins, and a scale. Making only ONE measurement (one time use only!) can you tell which bag contains the fake coins? Note: fake gold weighs .1 gram per coin less than real gold.

3. In you had only a 3cup measure and a 5cup measure can you measure out 4 cups of water evenly? You cannot use any other vessel.