SOLUTION: My question is a systems d=rt. I have tried but failed to solve it. A salmon swims 200m in 12 minutes downstream. Swimming in the opposite direction it takes that fish 15 minut

Algebra ->  Coordinate Systems and Linear Equations -> SOLUTION: My question is a systems d=rt. I have tried but failed to solve it. A salmon swims 200m in 12 minutes downstream. Swimming in the opposite direction it takes that fish 15 minut      Log On


   

Question 915070: My question is a systems d=rt. I have tried but failed to solve it.
A salmon swims 200m in 12 minutes downstream. Swimming in the opposite direction it takes that fish 15 minutes to travel the same distance. Find the rate of swimming for the fish and the rate of the current. Thanks in advance and hopefully I get the answer (or at least help) fast.
Found 2 solutions by josgarithmetic, richwmiller:
Answer by josgarithmetic(39618) About Me  (Show Source):
You can put this solution on YOUR website!
r, salmon rate when no stream current
c, stream current speed

_________________rate_________time_________distance______equation
downstream_______r+c__________12___________200___________%28r%2Bc%29%2A12=200
upstream_________r-c__________15___________200___________%28r-c%29%2A15=200

Two linear equation in the two unknown variables, r and c.

Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!

r*t=d
with the current
(r+c)*12=200
(r+c)=200/12
r+c=16.6666667
against the current
(r-c)*15=200
(r-c)=200/15
r-c=13.3333333
r+c=16.6666667
add
r+r=16.6666667+13.3333333
2r=30
r=15 mpm rate
15-c=13.3333333
c=15-13.3333333
c=1.66666667 mpm current
check
(15+1.66666667)*12=200
16.6666667*12=200
200.0=200
ok
(r-c)*15=200
(15-1.66666667)*15=200
13.3333333*15=200
200.0=200
ok
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