SOLUTION: I have finals coming up and I still don't understand much of Rational Expressions. Can you help me with a few questions?
1.) How much water must be evaporated from a 300L tank o
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1.) How much water must be evaporated from a 300L tank o
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Question 704627: I have finals coming up and I still don't understand much of Rational Expressions. Can you help me with a few questions?
1.) How much water must be evaporated from a 300L tank of a 2% salt solution to obtain a 5% solution?
2.) A town's old street sweeper can clean the streets in 60h. The old
sweeper together with the new one can clean the streets in 15h. How long would it take the new sweeper to do the job alone?
Thanks! Found 2 solutions by josgarithmetic, ankor@dixie-net.com:Answer by josgarithmetic(39614) (Show Source):
You can put this solution on YOUR website! Problem Number 2:
Rate of old sweeper = 1 job per 60 hours
Rate of new sweeper = unknown, R
Rate of both old and new together = 1 job per 15 hours
, street jobs per hour. , again this is street jobs per hour.
You might want this as the reciprocal, 20 hours per job.
You can put this solution on YOUR website! 1.) How much water must be evaporated from a 300L tank of a 2% salt solution to obtain a 5% solution?
Let w = amt of water to be evaporated
Write an amt of salt equation, amt of salt remains the same only the percent changes
.02(300) = .05(300-w)
6 = 15 - .05w
.05w = 15 - 6
.05w = 9
w = 9/.05
w = 180 L of water to be allowed to evaporate
:
Check this
.02(300) = .05(300-180)
6 = 6; confirms our solution
:
:
2.) A town's old street sweeper can clean the streets in 60h.
The old sweeper together with the new one can clean the streets in 15h.
How long would it take the new sweeper to do the job alone?
:
let n = time required by the new sweeper alone
let the completed job = 1
:
A shared work equation
:
old guy + new guy = swept street + = 1
multiply by 60n to clear the denominators, resulting in:
15n + 60(15) = 60n
900 = 60n - 15n
900 = 45n
n = 900/45
n = 20 hrs for the younger, more dynamic guy, to do the job
:
See if this checks out
15/60 + 15/20
1/4 + 3/4 = 1
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