Cassandra rows a boat downstream for 120 miles. The return trip upstream took 18 hours longer. If the current flows at 3 mph, how fast does Cassandra row in still water?

Answer 1

d= rt

distance = rate of speed times time traveled

still water speed for the boat is 7 mph

downstream 7+3 = 10 mph

for 12 hours

10 x 12 = 120 miles

upstream 7-3 = 4 mph

for 12+18 = 30 hours

4 x 30 = 120 miles