SOLUTION: How much pure gold (24K) must be mixed with 70% gold to get 30 grams (g) of 80% gold? Express in decimal form rounded to one decimal place.

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Question 1157076: How much pure gold (24K) must be mixed with 70% gold to get 30 grams (g) of 80% gold? Express in decimal form rounded to one decimal place.
Found 2 solutions by josgarithmetic, MathTherapy:
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
g of 100%
30-g of 70%
100g%2B70%2830-g%29=80%2A30
-
100g-70g%2B70%2A30=80%2A30
g%28100-70%29=30%2880-70%29
highlight_green%28g=30%28%2880-70%29%2F%28100-70%29%29%29
g=30%281%2F3%29
highlight%28g=10%29

Answer by MathTherapy(10552) About Me  (Show Source):
You can put this solution on YOUR website!

How much pure gold (24K) must be mixed with 70% gold to get 30 grams (g) of 80% gold? Express in decimal form rounded to one decimal place.
Let amount of pure gold be G

Then amount of 70% gold = 30 - G

We then get: G + .7(30 - G) = .8(30)

G + 21 - .7G = 24

G - .7G = 24 - 21

.3G = 3

Amount of pure gold, or highlight_green%28matrix%281%2C6%2C+G%2C+%22=%22%2C+3%2F.3%2C+%22=%22%2C+10%2C+g%29%29