SOLUTION: A dairy farmer wants to mix a 55% protein supplement and a standard 25% protein ration to make 1200 pounds of a high-grade 45% protein ration. How many pounds of each should he use

Algebra ->  Expressions-with-variables -> SOLUTION: A dairy farmer wants to mix a 55% protein supplement and a standard 25% protein ration to make 1200 pounds of a high-grade 45% protein ration. How many pounds of each should he use      Log On


   



Question 1152731: A dairy farmer wants to mix a 55% protein supplement and a standard 25% protein ration to make 1200 pounds of a high-grade 45% protein ration. How many pounds of each should he use?
Found 3 solutions by josmiceli, MathTherapy, greenestamps:
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +a+ = pounds of 55% mix needed
Let +b+ = pounds of 25% mix needed
------------------------------------------------
(1) +a+%2B+b+=+1200+
(2) +%28+.55a+%2B+.25b+%29+%2F+1200+=+.45+
----------------------------------------
(2) +.55a+%2B+.25b+=+540+
(2) +55a+%2B+25b+=+54000+
(2) +11a+%2B+5b+=+10800+
Multiply both sides of (1) by +5+
and subtract (1) from (2)
(2) +11a+%2B+5b+=+10800+
(2) +-5a+-+5b+=+-6000+
------------------------------
+6a+=+4800+
+a+=+800+
and
(1) +a+%2B+b+=+1200+
(1) +800+%2B+b+=+1200+
(1) +b+=+400+
----------------------------
800 pounds of 55% mix are needed
400 pounds of 25% mix are needed
----------------------------------------
check:
(2) +%28+.55a+%2B+.25b+%29+%2F+1200+=+.45+
(2) +%28+.55%2A800+%2B+.25%2A400+%29+%2F+1200+=+.45+
(2) +%28+440+%2B+100+%29+%2F+1200+=+.45+
(2) +540+=+.45%2A1200+
(2) +540+=+540+
OK

Answer by MathTherapy(10553) About Me  (Show Source):
You can put this solution on YOUR website!

A dairy farmer wants to mix a 55% protein supplement and a standard 25% protein ration to make 1200 pounds of a high-grade 45% protein ration. How many pounds of each should he use?
Let amount of 55% protein be F
Then amount of 25% protein = 1,200 - F
We then get: .55F + .25(1,200 - F) = .45(1,200)
.55F + 300 - .25F = 540
.55F - .25F = 540 - 300
.3F = 240
F, or amount of 55% protein to use = highlight_green%28matrix%281%2C4%2C+240%2F.3%2C+%22=%22%2C+800%2C+lbs%29%29
Amount of 25% protein to use = highlight_green%28matrix%281%2C4%2C+%221%2C200%22+-+800%2C+%22=%22%2C+400%2C+lbs%29%29
That's IT!! Nothing that COMPLEX or LENGTHY!!

Answer by greenestamps(13200) About Me  (Show Source):
You can put this solution on YOUR website!


Certainly if you are going to use a formal algebraic method to solve the problem you should use a single variable; the amount of work you need to do will be much less than if you use two variables.

Or here is a non-algebraic method that requires far less effort than the single variable algebraic method.

Consider the three percentages on a number line; specifically, look at where the 45% of the mixture lies in relation to the 25% and 55% of the two ingredients.
    25 -------------- 45 ------- 55

Using any number of possible different calculations, find that 45% is two-thirds of the way from 25% to 55%.

That means 2/3 of the mixture needs to be the 55% ingredient.

ANSWER:
55% protein supplement: 2/3 of 1200 pounds, or 800 pounds
standard 25% protein ration: 1/3 of 1200 pounds, or 400 pounds