The riddle plays on the assumption that surgeons are male. The surgeon is the boy’s mother, which answers the riddle.
Light the first rope at both ends. It will burn completely in 30 minutes since it’s burning from both sides, despite the irregular burn rate.
At the same time, light the second rope at one end. When the first rope is fully burned (after 30 minutes), immediately light the other end of the second rope.
The second rope will now burn in 15 minutes because it is burning from both ends, so you’ve measured 45 minutes in total.
If the rate at which water is leaking out of the hole is the same as the rate at which it’s being added, the barrel will never fill because the incoming water is continuously being drained out.
The number "seven" is an odd number, and if you remove the letter "s," it becomes the word "even," which is even.
This is a wordplay riddle. If you add four and five together, you get nine.
