Question 632285
let boat speed = x mph
plane speed = 20 x


Time forward + time return = 42 hours

distance one way = 640 miles

time = d/r

640/x + 640/20x= 42

LCD = 20x
(640*20 +640)/20x= 42
12800 +640= 42*20x

13440= 840x

x= 13440/840

x= 16 mph  the speed of boat

speed of plane = 16*20 = 320 mph

m.ananth@hotmail.ca