a 480 pound alloy containing 30% silver was mixed with an alloy containing 55% silver to get an alloy containing 40% silver. How many pounds of the 55 alloy were used?
Let x be the number of pounds of the 55% silver alloy used.
The amount of silver in the 480 pound alloy is 0.3 * 480 = 144 pounds.
The amount of silver in the x pound alloy is 0.55x.
When the two alloys are mixed, the total amount of silver is 144 + 0.55x.
The total weight of the new alloy is 480 + x pounds.
Since the new alloy contains 40% silver, we can set up the following equation:
0.4(480 + x) = 144 + 0.55x
192 + 0.4x = 144 + 0.55x
0.15x = 48
x = 320 pounds
Therefore, 320 pounds of the 55% silver alloy were used.