How do we measure forty-five minutes using two identical wires, each of which takes an hour to burn? We have matchsticks with us. The wires burn non-uniformly. For example, the two halves of the wire might burn in 10 minutes and 50 minutes, respectively.
Check if you were right - full answer with solution below.
Solution: If a wire takes exactly 60 minutes to burn from one end, then lighting it from both ends causes it to burn out in 30 minutes, even though it burns non-uniformly.
- 0 minutes – Light wire 1 on both sides and wire 2 on one side.
- 30 minutes – Wire 1 will be burnt out. Light the other end of the wire 2.
- 45 minutes – Wire 2 will be burnt out. Thus 45 minutes is completely measured.