Question 61093
The current in ther lazy river moves at a rate of 4mph. Monica'sdinghy motors 6mi upstream in the same time it take to motor 12mi downstream. What is the speed of the dinghy?
SPEED OF WATER = 4 MPH
LET SPEED OF DINGHY = S MPH
ITS SPEED UP STREAM = S-4 MPH
DISTANCE TRAVELED UPSTREAM = 6 M
TIME TAKEN = 6/(S-4) HRS..................1
ITS SPEED DOWN STREAM = S+4 MPH
DISATANCE TRAVELLED DOWN STREAM =  12 M
THEN TIME TO TRAVEL UPSTREAM = 12/(S+4) HRS...............2
TIMES ARE EQUAL 
6/(S-4) = 12/(S+4)
12(S-4)=6(S+4)
12S-48=6S+24
6S=72
S=12 MPH