Expert: Scott A Wilson - 1/30/2010

Question
One type of antifreeze is 40% glycol, and another type of antifreeze is 60% glycol. How much of each kind should be used to make 100 gallons of antifreeze that is 48% glycol?

Please help..thanks. :)

Answer
The 1st type is 40% gycol and the 2nd type s 60% glycol.

Note that 48% is only 8% over 40% and 12% under 60%.

That means that if we took them with a ratio of 12:8, the result wold be 48%.

Since 12 + 8 = 20, and we want 100 gallons, multiply both ratios by 100/20 = 5.

That means our 12:8 is 60 gallons : 40 gallons.

So if we take 60 gallons at 40%, that is 24 gallons of glycol and 36 gallons of water.
If we take 40 gallons at 60%, that is 24 gallons of glycol and 16 gallons of water.

Adding these together gives 48 gallons of glycol and 52 gallons of water, for 100 gallons total.
We have 48 gallons of glycol out of 100 gallons total, which is 48%.