im going with 20 because u'd have to cut the board twice so just double the time it took to make 1 cut.
Math is hard. Omw back to the kitchen now.
Nice question, I answered with 20 too!
It depends on how long the 2nd cut is. If you cut the board into three equal pieces it's 20 minutes. If not, it could be 15 because the 2nd cut is a shorter distance.