How much water must be added to 12 L of a 40% solution of alcohol to obtain a 30% solution?

A. .5 L
B. 5 L
C. .4 L
D. 4 L

Question

How much water must be added to 12 L of a 40% solution of alcohol to obtain a 30% solution?

	A.	.5 L
	B.	5 L
	C.	.4 L
	D.	4 L

anonymous · Answer

almost identical to the last one

mathmate · Answer

The total volume should be 12l*(40%/30%)=16l
So how much water must be added?

parthkohli · Answer

@emmat9795 Please close a problem only when you finish with it. Thanks :)

anonymous · Answer

you have $.4\times 12=4.8$ L of alcohol to begin with
if you add say $x$ liters of  water you will still have 4.8 L of alcohol but now you will have 
$12+x$ liters of liquid
you want this to be 30% alcohol, so set $4.8=0.3(12+x)$ and solve for $x$

anonymous · Answer

whatever @ParthKohli