A goldsmith mixed 30 g of a 40% gold alloy with 60 g of a 25% gold alloy. What is the percent concentration of the resulting alloy?

Question

this is a word problem that Icant figure out

Answer 1

Start with what you know, possibly translating it into a more useful form than what you're given.  For example, you are told that you start with 30g of a 40% gold alloy.  What does that actually mean?  It means that you have 30g of metal, and of that metal, 40% is gold.  How much gold is that?  Just multiply: .4*30g=12g.  So you have 12 g of gold.  Do the same for the other hunk of metal, and you get 15g of gold.  So when you melt and mix the two hunks of metal together, you have 27g of gold, and 90g of metal.  So now you only have to ask, what percentage of the metal is gold?  Just divide for the answer: 27g/90g = .3 = 30%.

Answer 2

40%(30)+25%(60)=(90)x, where x is the percent

0.4*30+0.25*60=90x

12+15=90x

27=90x

27/90=x

3/10=x

x=3/10=30/100=30%