Answer:
<u>135.73 ounces</u> of a silver alloy that costs $5.50 per ounce should be mixed.
Step-by-step explanation:
Given:
A silver alloy that costs $5.50 per ounce should be mixed with one that costs $7.00 per ounce to make a new 30 ounce alloy that costs $6.40 per ounce.
Now, to find the ounces of silver alloy.
Let the silver costs $5.50 per ounce be
And the silver costs $7.00 per ounce be
So, the total ounce make a new alloy:
....(1)
Now, the total costs of silver alloy:
Putting the value of from equation (1) in the place of
:
<em>Subtracting both sides by 210 we get:</em>
<em>Dividing both sides by -1.5 we get:</em>
Therefore, 135.73 ounces of a silver alloy that costs $5.50 per ounce should be mixed.