a gambling boat on the mississippi river can go 60 miles up river in the same amount of time that it takes it to go 140 miles down river, if the rate of the

Question

current for the river is 8mph,what is the speed of the boat in still water?

Answer 1

Let the speed of boat be V. Then we can set up the equation:

 

140/(V+8)=60/(V-8)

 

Or

 

7/(V+8)=3/(V-8)

 

Cross-multiply to get:

 

7V-56=3V+24

 

4V=80

 

V=20 mph

 

Answer: 20 mph

Answer 2

Hi Tanisha;

x=speed, in m/h, of boat in still water
(x-8 m/h)(60 m)=(x+8 m/h)(140 m)
(x+8) is the faster speed which generated the greater distance of 140 m.
The units m/h and m are on both sides of the equation. Therefore, these cancel.
(x-8)(60)=(x+8)(140)
60x-480=140x+1120
Let's subtract 60x from both sides...
-60x+60x-480=140x+1120-60x
-480=80x+1120
Let's subtract 1120 from both sides...
-1120+-480=80x+1120-1120
-1600=80x
Let's divide both sides by 80...
-1600/80=80x/80
-20=x

 

In still-water, it will travel downstream at 20 mph.

Answer 3

distance=rate*time

d=r*t

60=(r-8)*t    up river

140=(r+8)*t    down river

60/(r-8)=140/(r+8)  because both expressions are equal to t

cross multiply

60(r+8)=140(r-8)

60r+480=140r-1120

480+1120=140r-60r

1600=80r

20=r

r = 20 mph, the speed of the boat

check:60/(20-8)=140/(20+8)

          60/12=140/28

                 5=5