Word Problem

[Bruu3465]

A motorboat can travel upstream on a river at 12mph and downstream at 20 mph. How far upstream can the boat travel if it leaves at 8:00 A.M. and must return by noon?

 

[arthur ohlsten]

let x be the distance upstream the boat travels
the time it spends traveling in hours is
x/12 + x/20
this time must equal 12-8 or 4 hours
x/12 + x/20 =4
20x+12x=4[20][12]
32x= 80[12]
x=30 miles

Arthur