Question

Stacy rowed across the lake with her friend Rainey (in the same boat) at a rate of 4 mph. Rainey then rowed back at a rate of 3 mph. If the lake is 6 miles across, how long did it take them to complete their trip?

Answer 1

According to my various methods it took them 12 hours to reach the end

Answer 2

4 miles per hour
6/4 = 1.5

3 miles per hour
6/3= 2 

1.5+ 2 = 3.5 mps