SOLUTION: A metal alloy is 30% nickel. Another metal ally is 70% nickel. The two alloys are mixed to produce 20kg of a metal alloy that is 48% nickel. How much of each metal alloy is used.

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: A metal alloy is 30% nickel. Another metal ally is 70% nickel. The two alloys are mixed to produce 20kg of a metal alloy that is 48% nickel. How much of each metal alloy is used.      Log On


   



Question 980590: A metal alloy is 30% nickel. Another metal ally is 70% nickel. The two alloys are mixed to produce 20kg of a metal alloy that is 48% nickel. How much of each metal alloy is used.
Found 2 solutions by ikleyn, josmiceli:
Answer by ikleyn(52814) About Me  (Show Source):
You can put this solution on YOUR website!

Let  x  be the mass of the first alloy  (first piece)  in kilograms,  and let  y  be the mass of the second alloy  (second piece)  in kilograms.

Then you have first equation

x + y = 20.

The first alloy contains  0.3*x  kilograms of nickel,  and the second alloy contains  0.7*y  kilograms of nickel.  Therefore the mix contains  0.3*x + 0.7*y  kilograms of nickel.

It gives you the second equation

0.3*x + 0.7*y = 0.48*20 = 9.6.

So,  you have the system of two linear equations in two unknowns

system%28x+%2B+y+=+20%2C%0D%0A0.3%2Ax+%2B+0.7%2Ay+=+9.6%29.

Solve yourself this system.


Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +a+ = kg of 30% alloy needed
Let +b+ = kg of 70% alloy needed
+.48%2A20+=+9.6+ kg of nickel in 48% alloy
---------------------
(1) +a+%2B+b+=+20+
(2) +%28+.3a+%2B+.7b+%29+%2F+20+=+.48+
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(2) +.3a+%2B+.7b+=+9.6+
(2) +3a+%2B+7b+=+96+
Multiply both sides of (1) by +3+ and
subtract (1) from (2)
(2) +3a+%2B+7b+=+96+
(1) +-3a+-+3b+=+-60+
-----------------------
+4b+=+36+
+b+=+9+
and
(1) +a+%2B+b+=+20+
(1) +a+=+11+
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11 kg of 30% alloy is needed
9 kg of 70% alloy is needed
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check:
(2) +%28+.3a+%2B+.7b+%29+%2F+20+=+.48+
(2) +%28+.3%2A11+%2B+.7%2A9+%29+%2F+20+=+.48+
(2) +%28+3.3+%2B+6.3+%29+%2F+20+=+.48+
(2) +9.6+=+20%2A.48+
(2) +9.6+=+9.6+
OK