Answer:
Answer: Add 315 gallons of 70% antifreeze to 90 gallons of 25% antifreeze to make a 60% mixture.
You need to end up a mixture that is 60% antifreeze.
You have 90 gallons of 25% antifreeze, which means it has .25*90 = 22.5 gallons of pure antifreeze mixed with a solvent (probably water).
.
You will add 'x' gallons of 70% antifreeze to make the 60% mixture.
So, at the conclusion, you will have (90+x) gallons 60% 'pure' antifreeze. That can be shown with the equation:
.
.25*90 + .7*x = .6*(90+x)
.
Multiply by 100 to eliminate fractions.
.
25*90 + 70x = 60(90 +x)
.
2250 + 70x = 5400 + 60x
.
10x = 5400 -2250
.
10x = 3150
.
x = 315 gallons of 70% antifreeze.
.
How much will you end up having on hand?
90 + 315 = 405 gallons
.
If it is 60% antifreeze, how much 'pure' antifreeze will be in the mixture?
.6*405 = 243
.
In the original 90 gallons, you have 22.5 gallons of pure antifreeze.
In the additional 315 gallons, you have .7*315 = 220.5 gallons.
22.5+220.5 = 243 gallons
Step-by-step explanation:
