Question 834344
Let {{{ x }}} = liters of 40% antifreeze needed
{{{ .4x }}} = liters of antifreeze in 40% solution
{{{ .1*4 = .4 }}} liters of antifreeze in 10% solution
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{{{ ( .4 + .4x ) / ( x + 4 ) = .35 }}}
{{{ .4 + .4x = .35*( x + 4 ) }}}
{{{ .4 + .4x = .35x + 1.4 }}}
{{{ .05x = 1 }}}
{{{ x = 20 }}}
20 liters of 40% antifreeze are needed
check:
{{{ ( .4 + .4x ) / ( x + 4 ) = .35 }}}
{{{ ( .4 + .4*20 ) / ( 20 + 4 ) = .35 }}}
{{{ 8.4 = .35*24 }}}
{{{ 8.4 = 8.4 }}}
OK