SOLUTION: How much 7% color paint would I need to add to white paint to get a 3% color?

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Question 165460: How much 7% color paint would I need to add to white paint to get a 3% color?
Answer by ptaylor(2198) About Me  (Show Source):
You can put this solution on YOUR website!
FIRST OF ALL, WE NEED TO KNOW HOW MUCH WHITE PAINT THAT YOU HAVE TO START WITH. SINCE WE DON'T KNOW, WE'LL LET "A" REPRESENT THE AMOUNT OF WHITE PAINT AND YOU CAN ADD IN THE ACTUAL VALUE.
Let A=amount of white paint the you have to start with
And let x=amount of 7% paint that is added
Now we know that the amount of pure color in the 7% paint that is added(0.07x) plus the amount of pure color in the white paint(0) has to equal the amount of pure color in the final mixture (0.03(A+x)), so our equation to solve is:
0.07x=0.03(A+x) get rid of parens (distributive law)
0.07x=0.03A+0.03x subtract 0.03x from each side
0.07x-0.03x=0.03A+0.03x-0.03x collect like terms
0.04x=0.03A divide each side by 0.04
x=0.75A
CK
0.07*0.75A=0.03(A+0.75A)
0.525A=0.03*1.75A
0.525A=0.525A

Hope this helps---ptaylor