Julie and eric row their boat (at a constant speed) 18 miles downstream for 3 hours by the current. rowing at the same rate, the trip back against the current takes 6 hours. find the rate of the boat in still water

the crews rowing rate is 6 mph and the rate of the current is 3 mph

Step-by-step explanation:

v the crew rowing rate

u rate of the current

downstream  v + u = 13.5/1.5 = 9 mph

upstream      v - u = 13.5/4.5 = 3 mph

u = 9 - v

v - ( 9 - v ) = 3

v - 9 + v = 3

2 v = 12

v 6 mph,   u 9 - 6 = 3 mph

hello from mrbilldoesmath!

answer:

25x^2 + 90x + 84

discussion:

mn(x) = m(n(x)) = m( 5x + 9) =

(5x + 9)^2 + 3 =>

25x^2 + 90x + 9^2 + 3 =

25x^2 + 90x + 84                 (as 9^2 = 9*9 = 81)

which is the second choice

regards,  

mrb

p.s.   i'll be on vacation from friday, dec 22 to jan 2, 2019. have a great new year!