Friday, December 4, 2009

Yummy Puzzle

You are given eight jelly donuts. The donuts all weight the same amount except for one which is heavier. You have a balancing scale at your disposal. What's the minimum number of weightings required for you to pick out the heavy donut every time?
(from World's Best Logic Puzzles book by Seven Treasures Pub.)

Please explain your answer on our Family Puzzle Marathon site. Solve three puzzles and get a prize!


Anonymous said...


1st weighing: compare 4 & 4

2nd weighing: whichever side is heavier, compare 2 & 2

3rd: whichever side is heavier, compare 1 & 1

-Rachel T

Maria said...

Rachel T. Welcome back!
3 is pretty good, but you can do even faster...

Kim said...

Well, then it must be 2. So here's my thought:

First weigh 3 and 3 -- if they are the same, then one of the other two is the culprit. Compare them.

If they are not the same, then you know it's one of those three. Weigh one against a second. If they are the same, then the third is the heavier one. If they are not, then the heavier one is the one.

Maria said...

Kim rocks!
new puzzle on Saturday

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