Two people are cutting wood. They cut wood in 8 minutes. How many minutes it takes to cut the wood into 4 pieces?

16 minutes

Reason:

• To go from 1 piece to 4 pieces you need 3 cuts (pieces = cuts + 1).
• With two people, they can cut in parallel, so in the first 8 minutes they can perform 2 cuts at once, giving 3 pieces.
• One more cut is still needed to reach 4 pieces; that takes another 8 minutes.
• Total time = 8 + 8 = 16 minutes.

Assumes: each cut takes the same amount of time, and two cuts can be made simultaneously (one by each person).