Question 737783
Let {{{ x }}} = liters of 10% solution needed
{{{ .1x }}} = liters of salt in 10% solution
{{{ .15*20 = 3 }}} liters of salt in 15% solution
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{{{ ( .1x + 3 ) / ( x + 20 ) = .12 }}}
{{{ .1x + 3 = .12*( x + 20 ) }}}
{{{ .1x + 3 = .12x + 2.4 }}}
{{{ .02x = .6 }}}
{{{ x = 30 }}}
30 liters of 10% solution are needed
check:
{{{ ( .1x + 3 ) / ( x + 20 ) = .12 }}}
{{{ ( .1*30 + 3 ) / ( 30 + 20 ) = .12 }}}
{{{ ( 3+ 3 ) / 50 = .12 }}}
{{{ 6 = .12*50 }}}
{{{ 6 = 6 }}}
OK