Question 683927
Let {{{ x }}} = m of soil with 55% sand needed
{{{ .55x }}} = m of sand in 55% soil
{{{ .25*1 = .25 }}} m of sand in 25% soil
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{{{ ( .55x + .25 ) / ( x + 1 ) = .35 }}}
{{{ .55x + .25 = .35*( x + 1 ) }}}
{{{ .55x + .25 = .35x + .35 }}}
{{{ .2x = .1 }}}
{{{ x = .5 }}}
.5 m of soil containing 55% sand must be added
check:
{{{ ( .55x + .25 ) / ( .5 + 1 ) = .35 }}}
{{{ ( .55*.5 + .25 ) / 1.5 = .35 }}}
{{{ .275 + .25 = 1.5*.35 }}}
{{{ .525 = .525 }}}
OK