Brain Teaser
Buford needs to
boil an egg for exactly 7 minutes. Any longer and it will
be too tough to eat without teeth. Any less, and it will
spill when he cracks it.
Unfortunately, the only
time pieces he has in his trailer are three hourglasses.
He has a 9-minute, an 11-minute and a 14-minute
hourglass.
How in tarnation can
he boil an egg for exactly 7 minutes using those three
hourglasses?
Solution
1
Start all 3 glasses at
the same time. When the 9-minute glass empties the
11-minute glass will have 2-minutes remaining and the
14-minute glass will have 5 minutes remaining. At the
same time, drop the egg in the water and turn one of
the 2 non-empty glasses on its side. When the other
glass empties, straighten the glass you tilted. Total
expired time = 9+7 = 16 minutes.
Solution
2
Throw the 14-minute hourglass away. Start the 9- and
11-minute glasses. When the 9-minute glass empties
flip it instantaneously and let it run until the remaining
2
minutes of the 11- minute empties. This leaves 7
minutes in the 9-minute glass. Drop the egg in your
already boiling water for the 7 minutes. Total expired
time = 9+2+7 = 18 minutes.
Our winner is . . .
Tricia Turk
Director of Business Development
Saxton-Ferris International
Minnetonka, MN