Answer:
40 gal
Step-by-step explanation:
The capacity of the machine is 140 gallons, and it must be filled.
In a 50% glycol solution, the amount of glycol in 140 gallons of solution is
50% * 140 gallons = 70 gallons.
Once the machine is full with 140 gallons of 50% glycol solution, it will have 70 gallons of glycol.
The machine now has 50 gallons of 60% glycol solution.
60% * 50 gallons = 30 gallons
The machine has now 30 gallons of glycol.
70 gal - 30 gal = 40 gal
You must add another 40 gallons of glycol.
