How many gallons of a 70% antifreeze solution must be mixed with 60 gallons of 25% antifreeze to get a mixture that is 60% antifreeze

antifreeze-solution

#1

How many gallons of a 70% antifreeze solution must be mixed with 60 gallons of 25% antifreeze to get a mixture that is 60% antifreeze?

You need to add ___ gallons of 70% antifreeze solution

Answer:

let x be the number of gallons of 70% antifreeze that needs to be added
given that x gallons of 70% anti freeze is added to 60 gallons of 25% anti freeze to get a mixture of 60% anti freeze.
x*.7+60*.25=(x+60)*.6
.7x+15=.6x+36
(.7-.6)x=36-15
.1x=21
x=21/.1=210
210 gallons of 70% anti freeze must be mixed.