SRL Archive - Mathematics

a. .75(x - .5) - 1.6 < .3

b. Soybean meal is 14% protein; cornmeal is 7% protein. How many pounds of each should be mixed together in order to get 280 pounds of 8% protein?

c. Find the solution (ordered pair)
a. .3x-.2y = 4
b. .4x + .3y = 73/19

d. Find the solution (ordered pair)
a. 7x + 6y = -10
b. -4x + y = 19

Please show work so I can actually learn how to do it!

Thank you!

a:
0.75x -0.4 -16 < 0.3
0.75x - 2 < 0.3
x - 2.666… < 0.4

x-2.666… = 0.4
x = 3.0666..

every x under 3.0666…
x < 3.0666…

Edit:
b:
x = amount of soybean meal
y = amount of corn meal

(0.14xr + 0.07yr) / (yr+xr) = 0.08
0.14xr + 0.07yr = 0.08yr + 0.08xr
0.01yr = 0.06xr
yr = 6xr ratio between soybean and corn

x = 280 / 7 * 1
x = 40

y = 280 / 7 * 6
y = 240

check:

x * 0.14 = total amount of protein in soybean meal
y * 0.07 = total amount of protein in corn meal

40 * 0.14 = 5.6
240 * 0.07 = 16.8

total amount of protein = 22.4
280 * 0.08 = 22.4

From: masterBB
a:
0.75x -0.4 -16 < 0.3
0.75x - 2 < 0.3
x - 2.666… < 0.4

x-2.666… = 0.4
x = 3.0666..

every x under 3.0666…
x < 3.0666…

Wrong answer. Just plug it back in and you'll see it doesn't work.
Anyways, the way to do #a and #b is attached. C and D use the same concepts as B so I didn't bother.

Thanks I see my problem

a:
0.75x -0.375 -1.6 < 0.3
0.75x - 1.975 < 0.3
x - 2.6333… < 0.4

x-2.6333… = 0.4
x = 3.0333..

every x under 3.0333…
x < 3.0333…

Should use my calculator after 11 in the evening.

Just system of equations.. u can either substitute one into the other or u can multiply them by eachother so that u get an LCF.. Minus or add them and either the X Or Y's should be 0.. then substitute the value back in and bam.. solved..

a. 7x + 6y = -10
b. -4x + y = 19

x = -4, y = -3

How? Solve by LCF or substitution.. whatever u choose:
-28x - 24y = 40
-28x + 7y = 133

Add them in this case to make x = 0
0x - 31y = -93
y = 3

Sub the value back into either equation to get x:
7x + 6(3) = -10
7x = -10 - 18
7x = -28
x = -4