Question

A boat traveled downstream a distance of 80 mi and then came right back. If the speed of the current was 8 mph and the total trip took 5?

Answer 1

Answer: Average speed of boat = 32mph

Step-by-step explanation: Full question: 5 hours 20mins. Find the average speed of the boat

Let average speed of boat be mph

Let time to travel downstream = 80/(x + 8 )

Let time to travel upstream = 80/( x - 8)

Total time = 51/3 hrs=16/3 hrs

80/(x +8) +80/(x-8) = 16/3

Multiply both sides with3(×+8)(x-8)

(X+8)(x-8) = (x+8)(x-8)/16

15(2x)=x^2-64

X^2 -30x - 64 =0

Factorizing,you get

(x - 32)(x + 2) => ×=32 or x= -2

x = 32mph