Answer:
60 mL
Step-by-step explanation:
Let x represent the amount of pure alcohol to be added (in mL). The total amount of alcohol in the mix is ...
30% × 360 mL + 100% × x mL = 40% × (x +360) mL
108 + x = 0.4x + 144 . . . . simplify
0.6x = 36 . . . . . . . . . . . . . subtract 0.4x +108
36/0.6 = x = 60 . . . . . . . . divide by the coefficient of x
60 mL of pure alcohol must be added to 360 mL of 30% to raise the concentration to 40%.
