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put this solution on YOUR website! assuming 100% acid....
{100% }* x + [ 20% ]* (40 ml ) = ( 28 %) ( 40 + x )
where x = amount of acid in ml....
40 + x = total ml of 28% solution ...
convert % to decimal.... [ move decimal 2 times left on each ...]
1x + .20 * 40 = .28 ( 40 + x)
x + 8 = 11.2 + .28x
.72x = 3.2 ..... x = 4.44 ml
