<PRE><B>Question 850090</B>
a lot of brass scrap weighing 350 kg contains 30% zinc.
 how many kg of zinc must be added in melting to raise the percentage of zinc to 40%?
:
let z = amt of zinc required to do this
:
A typical mixture equation
.30(350) + z = .40(x+350)
105 + z = .4z + 140
z - .4z = 140 - 105
.6z = 35
z = 35/.6
z = 58{{{1/3}}}kg of zinc required
:
:
Check this
.30(350) + 58.333 = .4(58.33+350)</PRE>