Question

Tina would like to melt down her existing gold jewelry to make a 20 ounce gold necklace that is 90% pure gold. After melting her jewelry, she is left with two batches. One batch is 75% pure. The other batch is 96% pure. How much of the 96% pure melted gold should Tina mix with the 75% pure melted gold to obtain 20 ounces of 90% pure gold?

Answer 1

@Luigi0210 @iGreen @CO_oLBoY

Answer 2

weight of 96% batch : weight of 75% batch
= 90-75 : 96-90
= 15:6
=5:2
Alternatively, let x=fraction of 96%, and 1-x = fraction of 75%
Then solve for x in
0.96x+0.75(1-x)=0.9
0.21x=0.15
x=5/7
So 5/7 of 96%, and 2/7 of 75% (same as 5:2)

Answer 3

thanks!

Answer 4

You're welcome! :)