Solution Step 0/0
You must boil an egg for exactly 5 minutes. All you have is a 3-minute hourglass and a 4-minute hourglass.
Can you figure out how to use these two hourglasses to measure 5 minutes?
How many times will you turn the 4-minute hourglass upside-down?
Can you figure out how to use these two hourglasses to measure 5 minutes?
How many times will you turn the 4-minute hourglass upside-down?
Explanations
Step 1. Start the 3- and 4-minute hourglasses when the egg is dropped into the boiling water.Step 2. When the sand stops running in the 3-glass, turn it over.
Step 3. When the sand stops running in the 4-glass, turn the 3-glass again.
Step 4. When the sand stops running again in the 3-glass, 5 minutes will have elapsed.
Interesting enough, the 4-minute hourglass is not tuned upside-down even a single time. Hence, the question: is it needed at all? Yes, its role is very crucial at Step 3 to set the final 5th minute in the moment all its sand stops running.
Check 0 times
Check 1 time
Check 2 times
Check 3 times
