Question 66436
Let x = the amount of mixture I want to remove
Then .1*x = the amount of antifreeze in the mixture
Then x = the amount of antifreeze I want to put back in,
making 12 = the amount of mixture once again
stated in a formula,
{{{(.1*12 - .1*x + x) / 12 = .4}}}
{{{(1.2 + .9x) / 12 = .4}}}
{{{4.8 = 1.2 + .9x}}}
{{{.9x = 3.6}}}
{{{x = 4}}}
I say that 4 quarts of 10% mixture must be removed and
replaced with pure antifreeze. Check this
4 + 8 = 12, so
{{{(4 + .1*8) / 12 = .4}}}
{{{4.8 / 12 = .4}}}
{{{.4 = .4}}}