boat race start time

I don’t understand this problem. Please help me?

Two boats start together and race across a 62 km wide lake and back. Boat A goes across at 62 km/h and returns at 62 km/h. Boat B goes across at 31 km/h, and its crew, realizing how far behind it is getting, returns at 93 km/h. Turnaround times are negligible, and the boat that completes the round-trip first wins.

(a) Boat A wins- distance / time = rate….. time = distance / rate.

Boat A to the far shore:
rate = 62km/h
distance = 62km
time = 1 hour. since the rate is the same, the boat will complete the trip in 2 hours.

Boat B to the far shore:
rate = 31km/h
distance = 62km
time = 2 hours
You know right here that Boat A will be back by the time Boat B gets to the far shore.

so the distance is 62KM

(b) average velocities:
Boat A: since it’s traveling at 62km/h there and back, it’s easy

Boat B: a little more tricky.
You know it takes 2 hours to get there going at 31km/h
And it takes 62/93 = 2/3 hours to get back.

multiple each velocity by the ratios of the total time and you will get the answer.

(31*2+ 92*2/3) / (2+2/3) = 46.5km/h

(TIME LAPSE) ANGUILLA DAY BOAT RACE (HD)

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