Answer:
67 gallons.
Step-by-step explanation:
To determine how many gallons of a 70% antifreeze solution must be mixed with 90 gallons of 15% antifreeze to get a mixture that is 60% antifreeze, the following calculation must be performed:
0.15 x 90 + 0.70 x 10 = 20.5 / 100 = 0.20
0.15 x 90 + 0.70 x 30 = 34.5 / 100 = 0.34
0.15 x 90 + 0.70 x 60 = 55.5 / 100 = 0.55
0.15 x 90 + 0.70 x 67 = 60.4 / 100 = 0.60
Thus, 67 gallons of 70% antifreeze solution will be needed to achieve a 60% mix of that solution.
