SOLUTION: one alloy is 50% silver and another is 20% silver. How much of each alloy is needed to make 100 kilograms of alloy which is 45% silver?

Question 845168: one alloy is 50% silver and another is 20% silver. How much of each alloy is needed to make 100 kilograms of alloy which is 45% silver?
Found 2 solutions by Alan3354, josmiceli:
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!

Do it like this one. Only the numbers are different.
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Amanda wants to make 8 gal. of a 20% saline solution by mixing together a 56% saline solution and a 8% saline solution. How much of each solution must she use?
================
e = amount of 8%
f = amount of 56%
---
e+ f = 8 (total solution)
8e + 56f = 20*8 (total saline)
---
e+ f = 8
e + 7f = 20
------------ Subtract
-6f = -12
f = 2
e = 6
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
Let = kg of 50% silver needed
Let = kg of 20% silver needed
---------------------------------
(1)
(2)
------------------------------
(2)
(2)
Multiply both sides of (1) by
and subtract (1) from (2)
(2)
(1)

and
(1)
(1)
(1)
83.333 kg of 50% silver is needed
16.667 kg of 20% silver is needed
-------------------------------
check:
(2)
(2)
(2)
(2)
close enough
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