Answer:
15 liters of the 10% acid solution must be used
55 liters of the 80% acid solution must be used
Step-by-step explanation:
Let the volume of the 10% acid solution be x
Let the volume of the 80% acid solution be y
The combination of the two solutions gives 70 liters
x + y = 70..............................(1)
The 70 liters solution is equivalent to 65%
10x + 80y = 70(65)
10x + 80y = 4550..........................(2)
Make x the subject of the formula in equation (1)
x = 70 - y...............................(3)
Substitute equation (3) into equation (2)
10(70 - y) + 80y = 4550
700 - 10y + 80y = 4550
70y = 4550 - 700
70y = 3850
y = 3850/70
y = 55 liters
Substitute y = 55 into equation (3)
x = 70 - 55
x = 15 liters