the hydro could go 40 miles per hour on a lake. The same boat could go 210 miles down the river in one-half the time it took to go 380 miles up the the river. how fast did the river flow.

(40+F) * time = 210 miles

( 40 - F) * 2 * time = 380, takes it twice as long to go 380 as 210 down stream

F is the flow and time it time.

solve the first for time = 210/(40+F)  sub into the second

use the quadratic on line solver

flow = 39.9

my equations turned out to be -21F^2 -19F + 32840 = 0

one real root and one negative root, discard the negative root.

210 miles per hour that how fast it can go

Step-by-step explanation: hope this help

just sum

10 + 10 = 20