Baffling Bath Water Puzzle - Solution
The Puzzle:
The cold faucet in my bath lets the water in at the rate of 15 litres per minute.
The hot faucet fills the bath at the rate of 10 liters per minute.
The plug hole lets the water out of the bath at the rate of 12 liters per minute.
The bath holds a maximum of 520 liters.
I turn both faucets on, but forget to put the plug in. After how many minutes will the bath begin to overflow?
Our Solution:
40 minutes.
Let's see how it's done:
Cold faucet fills at 15 liters / minute. Hot faucet fills at 10 liters / minute.
→ So water enters at 25 liters / minute. (15+10=25)
Plug hole empties at 12 liters / minute.
→ So bath fills up at 13 liters / minute. (25-12=13)
Bath holds 520 liters.
→ So bath overflows after 40 minutes. (520÷13=40)
(PS: don't try this at home, it just wastes fresh water!)