# physics

posted by
**john** on
.

Two boats start together and race across a 42 km wide lake and back. Boat A goes across at 42 km/h and returns at 42 km/h. Boat B goes across at 21 km/h, and its crew, realizing how far behind it is getting, returns at 63 km/h. Turnaround times are negligible, and the boat that completes the round-trip first wins.

(a) Which boat wins? (Or is it a tie?)

boat A

boat B

it's a tie

By how much?

km

(b) What is the average velocity of the winning boat?

km/h

I have no idea how to do th