Question

Can anyone please help me? You need a 20% alcohol solution. On hand, you have a 400 mL of a 15% alcohol mixture. How much pure alcohol will you need to add to obtain the desired solution?

Answer 1

you can set upthe equation as:

x mL of 100% alchohol + 400 mL of 15% alcohol = (x + 400) mL of 20% alcohol

Answer 2

you have 15% of 400 ml = \(.15\times 400=60\) ml of alcohol at present.
if you add say \(x\) ml of alcohol you will have \(60+x\) ml of alcohol and \(400+x\) ml of solution
you want \(400+x\) ml to be 20% alcohol, so set
\[60+x=.20(400+x)\] and solve for \(x\)

Answer 3

probably easiest to multiply by 10 on both sides to get
\[600+10x=2(400+x)\]
\[600+10x=800+2x\]
\[8x=200\] etc

Answer 4

THANK YOU VERY MUCH!

Answer 5

yw
hope steps are clear