Question 1017321

Julie and Eric row their boat (at constant speed ) 40 miles downstream for 4 hours, helped by the current. Rowing at the same rate, the trip back against the current takes 10 hours. Find the rate of the current.
<pre>Let speed in still water be S, and speed of current, C
Then, downstream speed equation is: {{{S + C = 40/4}}}______S + C = 10______S = 10 - C ------- eq (i)
Also, upstream speed equation is: {{{S - C = 40/10}}}______S - C = 4 ------- eq (ii)
10 - C - C = 4 ------- Substituting 10 - C for S in eq (ii)
      - 2C = 4 - 10
      - 2C = - 6
C or speed of current = {{{(- 6)/(- 2)}}}, or {{{highlight_green(matrix(1,2,3,mph))}}}