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put this solution on YOUR website!19. A certain chain saw requires a fuel mixture of 5.5% oil and the remainder gasoline. How many liters of 2.5% mixture and how many of 9% mixture must be combined to produce 40.0 liters of 5.5% mixture?
2.5% mixture DATA:
amount: x liters ; oil contents= 0.025x liters
9.0% mixture DATA:
amount: (40-x) liters ; oil contents= 0.09(40-x)=(3.6-0.09x) liters
5.5% Mixture DATA:
amount: 40 liters ; oil contents= 0.055(40)=2.2 liters
EQUATION:
oil cont. + oil cont. = 2.2 liters
0.025x + 3.6-0.09x = 2.2
-0.065x= -1.4
x=21.54 liters of 2.5% mixture
40-21.54 = 18.46 liters of 9% mixture
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20. Mary can row at the rate of 4 miles per hour in still water. Rowing downstream in a river, she can travel 3 times as far in 1 hour as she can rowing upstream. What is the rate of flow in the river?
Upstream DATA:
time= 1 hr. ; rate= (4- stream) mi/hr.; distance= rt=(4- s) mi
Downstream DATA:
time= 1 hr. ; rate= (4+ stream) mi/hr ; distance= rt=(4+s) mi
EQUATION:
distance downstream = 3*distance upstream
4+s = 3(4-s)
4+s = 12-3s
4s=8
s= 2 mph (stream speed is 2 mph)
In one hour she will go (4+2)= 6 mi downstream
In one hour she will go (4-2)= 2 mi upstream
Cheers,
Stan H.
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