Question 198833
(mg of nickel) / (mg of alloy) = 78%
Let {{{x}}}= mgs of metal with 45% nickel
{{{.45x + 6) / (x + 6) = .78}}}
{{{.45x + 6 = .78*(x + 6)}}}
{{{.78x - .45x = 6 - .78*6}}}
{{{.33x = 1.32}}}
{{{x = 4}}}
4 mg of the metal must be used
check:
{{{.45x + 6) / (x + 6) = .78}}}
{{{.45*4 + 6) / (4 + 6) = .78}}}
{{{1.8 + 6) / 10 = .78}}}
{{{7.8/10 = .78}}}
{{{.78 = .78}}}
OK