Question 271333
1)
D=RT
240=(R+9)T DOWNSTREAM TRIP.
T=240/(R+9)
160=(R-9)T UPSTREAM TRIP.
T=160/(R-9)
BECAUSE THE TIMES ARE THE SAME WE SET THE 2 EQUATIONS EQUAL & SOLVE FOR R.
240/(R+9)=160/(R-9) CROSS MULTIPLY
240(R-9)=160(R+9)
240R-2,160=160R+1,440
240R-160R=1,440+2,160
80R=3,600
R=3,600/80
R=45 MPH. IS THE SPEED OF THE BOAT IN STILL WATER.
PROOF:
240(45+9)=160(45-9)
240/54=160/36
4.444=4.444
2)
40/144=200/X
40X=144*200
40X=28,800
X=28,800/40
X=720 ESTIMATED NUMBER OF FISH IN THE LAKE.
3)
4*6/(4+6)
24/10=2.4 HOURS WHEN THEY WORK TOGETHER.