SOLUTION: Eight gallons of salt consists of 35% salt. It is the result of mixing a 50% solution with a 30% solution. How many gallons of each of the solutions was used? The corresponding mod

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Question 1081639: Eight gallons of salt consists of 35% salt. It is the result of mixing a 50% solution with a 30% solution. How many gallons of each of the solutions was used? The corresponding modeling system is
X+y=8
.5x+.3y=.35(8)

Found 2 solutions by josmiceli, ankor@dixie-net.com:
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
(1) +x+%2B+y+=+8+
(2) +.5x+%2B+.3y+=+2.8+
----------------------
(2) +5x+%2B+3y+=+28+
Multiply both sides of (1) by +3+
and subtract (1) from (2)
(2) +5x+%2B+3y+=+28+
(1) +-3x+-+3y+=+-24+
-----------------------
+2x+=+4+
+x+=+2+
and
(1) +2+%2B+y+=+8+
(1) +y+=+6+
---------------------
2 gallons of the 50% solution are needed
6 gallons of the 30% solution are needed
-------------------------------------
check:
(2) +.5x+%2B+.3y+=+2.8+
(2) +.5%2A2+%2B+.3%2A6+=+2.8+
(2) +1+%2B+1.8+=+2.8+
(2) +2.8+=+2.8+
OK

Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
Eight gallons of salt consists of 35% salt.
It is the result of mixing a 50% solution with a 30% solution.
How many gallons of each of the solutions was used?
The corresponding modeling system is
X + y = 8
.5x+.3y=.35(8)
:
X + y = 8
.5x+.3y= 2.8
multiply by 2, subtract from the 1st equation
x + y = 8
x +.6y = 5.6
---------------Subtraction eliminates x find y
0 + .4y = 2.4
y = 2.4/.4
y = 6 gallons of 30% solution
then
x = 2 gallons of 50% solution