SOLUTION: Hi! I am a little lost with the problem " how many gallons of pure antifreeze must be mixed with 30 gallons of 15% antifreeze to get a mixture that is 40% antifreeze" So far

Question 818362: Hi!
I am a little lost with the problem " how many gallons of pure antifreeze must be mixed with 30 gallons of 15% antifreeze to get a mixture that is 40% antifreeze"
So far I have multiplied 30 x .15 to get 4.5 gallons of pure antifreeze but am not sure where to go after that.
Thanks!
Rachel
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
how many gallons of pure antifreeze must be mixed with 30 gallons of 15% antifreeze to get a mixture that is 40% antifreeze"
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Equation:
alch + alch = alch
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0.15*30 + 1*x = 0.40(30+x)
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Multiply thru by 100 to get:
15*30 + 100x = 40*30 + 40x
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60x = 25*30
x = 12.5 gallons (amt. of pure solution needed)
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Cheers,
Stan H.
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