1. Assume that the types of metal allow we use are type A and type B
2. Assume we are using x kg of A and y kg of B
3. Then x+y=400, so y=400-x
also the weight of the aluminium in x kg of A and y kg of B are respectively:
[tex] \frac{15}{100}*x=0.15x [/tex] and
[tex]\frac{35}{100}*y=0.35y [/tex]
so the total sum of the aluminium is [tex]0.15x+0.35y=0.15x+0.35(400-x)=0.15x+140-0.35[/tex] [tex]=140-0.2x[/tex]
4. 27.5% of 400 is [tex] \frac{27.5}{100}*400=27.5*4= 110[/tex] kg
5. [tex]140-0.2x=110[/tex]
[tex]140-110=0.2x[/tex]
[tex]0.2x=30[/tex]
x=150 (kg),
y=400-x=400-150=250(kg)