SOLUTION: A boat can go 20 mi against a current in the same time that it can go 60 mi with the current. The current is 4 mph. Find the speed of the boat in still water.

Question 111165: A boat can go 20 mi against a current in the same time that it can go 60 mi with the current. The current is 4 mph. Find the speed of the boat in still water.
Answer by dolly(163) (Show Source): You can put this solution on YOUR website!

Let the speed of the boat be x mph
speed of the current = 4mph
so speed against the current = (x-4)mph
Distance traveled against the current = 20 miles
So time taken = distance/speed
= 20/(x-4)
Now speed with the current = (x+4)mph
Distance traveled with the current = 60 miles
So time taken = distance/speed
= 60/(x+4)
As the time taken is the same,
20/(x-4) = 60/(x+4)
Multiplying both the sides by (x-4)(x+4),
20(x+4) = 60(x-4)
==> 20x + 80 = 60x - 240
==> 240 + 80 = 60x - 20x [ collecting the like terms to one side]
==> 320 = 40x
==> 320/40 = x
==> 8 = x
Thus the speed of the boat in still water = 8mph
Best of luck!!!

RELATED QUESTIONS
A boat can go 20 miles against a current in the same time that it can go 60 miles with... (answered by josgarithmetic,stanbon)

A boat can go 20 miles against a current in the same time it can go 60 miles with the... (answered by rwm)

A boat traveling at 10 mph can go 20 miles against a current in the same time it can go... (answered by mananth)

A boat can go 10 miles against the current in the same it can go in 30 miles with the... (answered by ptaylor)

A motor boat traveling with the current can go 36 mi in 2 hr. Against the current it... (answered by richwmiller)

A boat takes 3 hrs to go 24 mi upstream against the current. It can go downstream with... (answered by ewatrrr)

a canoe can travel 15 mi/hr in still water. Going with the current, it can travel 20... (answered by stanbon)

A small motor on a fishing boat can move the boat at a rate of 14 mph in calm water.... (answered by ikleyn,greenestamps)

A small motor on a fishing boat can move the boat 6mph in calm water. When trolling in a... (answered by ewatrrr)