Question 180172

Distance(d) equals Rate(r) times Time(t) or d=rt;  r=d/t and t=d/r
Average speed of the boat for the entire trip =total distance divided by total time
Average speed =(48+48)/7=96/7=13.71 mph



Let r1=rate of the boat in still water
Let r2=rate of the current
Now we know that:
r1+r2= =48/3=16 mph----------------eq1
r1-r2=48/4=12 mph------------------eq2


add eq1 and eq2:

2r1=28  divide each side by 2
r1=14 mph------------------------------rate of the boat in still water
substitute r1=14 mph into eq1:
14+r2=16 subtract 14 from each side
r2=2 mph----------------------------------rate of the current

Hope this helps---ptaylor