Question

a motorboat, which can travel at 20 miles per hour in still water, takes 3/5 as long to travel downstream on a river from a to b, as to return. Find the rate of the rivers current.
speed of current --- x mph
distance ---- d miles

time to go downstream = d/(20+x)
time to go upstream = d/(20-x)

d/(20+x) = (3/5)d /(20-x)
divide both sides by d
1/(20+x) = 3/(5(20-x))
cross-multiply
60+3x = 100 - 5x
8x = 40
x = 5

the speed of the current is 5 mph

check:
suppose the distance is 100 miles
time to go downstream = 100/25 hrs = 4 hrs
time to go upstream = 100/15 = 20/3 hrs or
and (3/5)(20/3) = 4
Wow I wish I really understood this it sounds very interesting I wish I knew what y'all were talking about I wish some body would sit and explain it to me step by step but that will probably never happen

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