Four Friends A, B, C, D Need To Cross A Bridge

Four friends A, B, C, D Need to cross a bridge. A maximum of 2 peoples can cross at a time. It is night and they have just 1 lamp. People that cross the bridge must carry the lamp to see the way. A pair must walk together at the speed of slower person. Speeds of: A: 1 minute to cross bridge B: 2 minutes to cross bridge C: 7 minutes to cross bridge D: 10 minutes to cross bridge Now the question is... "What is the total minimum time required by all 4 friends to cross the bridge?"

#Quiz #Math