Question 879973
Let {{{ x }}} = kg of salt to be added
{{{ ( x + 5 ) / ( x + 5 + 35 ) = .4 }}}
{{{ x + 5 = .4*( x + 40 ) }}}
{{{ x + 5 = .4x + 16 }}}
{{{ .6x = 11 }}}
{{{ x = 18.333 }}}
18.333 kg of salt must be added
check:
{{{ ( x + 5 ) / ( x + 5 + 35 ) = .4 }}}
{{{ ( 18.333 + 5 ) / ( 18.333 + 5 + 35 ) = .4 }}}
{{{ 23.333 / 58.333 = .4 }}}
{{{ 23.333 = .4*58.333 }}}
{{{ 23.333 = 23.333 }}}
OK