math word problem

Question

a 15% batch of antiseptic that is 60% alcohol needs to be made. How much of a 30% alcoho antiseptic needs to be mixed with a 70% alcohol antiseptic to get the desired concentration for the 15 liters?

Answer 1

.7x + .3(15-x) = .6(15)

.4x = 9-4.5 = 4.5

x = 4.5/.4 = 11.25 liters of 70%

15-x = 3.75 liters of 30%

11.25/3.75=3

70-60=10

60-30=30

30/10=3