Question

Suppose that both 75% brass and 90% brass are available. How many pounds of each must be mixed to get 150 pounds of 87% brass? My book answers were x=30 pounds of 75% brass and y= 120 pounds of 90% brass. I wanted to know how to get that answer-- what is the equation is it x + y= 150 and ???????

Answer 1

30*0.75+120*0.9=150*0.87

Answer 2

so it is x*0.75+y*0.9=150*0.87

Answer 3

plus x+y=150

Answer 4

and if you solve these two equations than you get the result

Answer 5

I will key in with my scientific calculator. sounds right wait.... thank you

Answer 6

but the 30 and 120 is not given..... that is the answer at the back of my book

Answer 7

yes that is what confused me :D

Answer 8

hey he gave us a clue that brass is made of copper and zinc--- it means the other percentage to make a 100% is a zinc.

Answer 9

but now it is clear.
let x be the 75% one and y the 90%
than we want to make 150 pounds so x+y=150
also we want to get 87% brass
so x*0.75+y*0.9=150*0.87

Answer 10

y=150-x from first equation
you plug this into the second
0.75x +(150-x)*0.9=150*0.87

Answer 11

this gives 4.5=0.15x
so x=30
y=(150-x)=120

Answer 12

I am using scientific calculator using the command matrix....
ok let me do that.

Answer 13

calculators are bad... they do the work for you but you dont think

Answer 14

hehehe! yah.... but we are allowed to use it though in math modeling... i hate math ill be glad to get out in this class... its the only math i will be taking in nursing. thank goodness

Answer 15

:-)

Answer 16

did you get the result by the way?

Answer 17

not yet im still trying to figure out how to key in figures using matrix command.

Answer 18

I did not use a calculator and had the answer 10 minutes ago :-)

Answer 19

hahahaha!

Answer 20

thanks for your time andras--- I got the answer solving manually using your equation. But i donno how to key in the scientific calculator though--thanks for your effort. love this site.