If a silver alloy costs$6.50 per ounce is mixed with 30 ounces of silver alloy that costs $9 per ounce to make a mixture that costs $8 an ounce, how many of teh $6.50 an ounce alloy must be used?

Answer 1

6.5X + 9(30) = 8(30+X)

6.5X +270 = 240 + 8X

270-240 = 8X-6.5X

1.5X = 30

X = 30/1.5 =20 ounces of $6.50 alloy

9 is within 1 of 8

6.5 is within 1.5 of 8

1.5 is 3/2 of 1

30 is 3/2 of 20

You know you need more of $9 alloy since it's closer to $8

You need exactly 3/2 or 1.5 times more of the $9 alloy

30 is 1.5 times 20