Question 551089
Let {{{ x }}} = ft of 45% soil needed
{{{ .45x }}} = ft of sand in 45% soil
{{{ .15*1 }}} = ft of sand in 15% soil
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{{{ ( .45x + .15 ) / ( 1 + x ) = .35 }}}
{{{ .45x + .15 = .35*( 1 + x ) }}}
{{{ .45x + .15 = .35 + .35x }}}
{{{ .45x - .35x = .35 - .15 }}}
{{{ .1x = .2 }}}
{{{ x = 2 }}}
2 ft of soil containing 45% sand is needed
check answer:
{{{ ( .45*2 + .15 ) / ( 1 + 2 ) = .35 }}}
{{{ ( .9 + .15 ) / 3 = .35 }}}
{{{ 1.05 = 1.05 }}}
OK