Question

How many mg of a metal containing 45% nickel must be combined with 6mg of pure nickel to form an alloy containing 78% nickel?

Answer 1

let's call the mass of 45% nickel x.

45x + (100 x 6) = 78 x total mass

the total mass is 6 + x, so:

45x + 600 = 78(6 + x)
45x + 600 = 468 + 78x
600-468 = 78x - 45x
132 = 33x
x = 132/33
x = 4 g

hope this helps :)