Question

a store mixes Brazilian coffee worth $12 per kg and Venezuelan coffee worth $15 per kg. the mixture is to sell for $14 per kg. Find how much each should be used to make 348 kg mixture.

Answer 1

First, use a weighted average to find the relative amounts of Brazilian (b) and Venezuelan (v) coffee. They will be percents, so b+v=1.
12b + 15v = 14
Once you have those percents, you can use them to find out how much of each is in the 348kg mixture.

Answer 2

x=116 y=232?

Answer 3

Which one is B and which is V?

Answer 4

i think v=116 b=232? can someone verify with me

Answer 5

Well, telling you that those aren't right will kinda' tell you what is right. But, no, those are backwards. Can you see why?

Answer 6

oh yeah my bad I wrote it down the right way. just didnt type it the right way

Answer 7

I'm going to try a slight variation on dmancine's method; let's see...

Let b=pounds of Brazilian coffee needed
let v==pounds of Venzuaelan coffee needed

then the two can be related by total weight:
b+v=348 [eqn 1]

they can also be reltaed by cost
12b+15v=14(b+v)
or
-2b+v=0
solving for v (to use substitution)
v=2b [eqn 2]

Now sub 2b for v in [eqn 1]
b+2b=348
3b=348
b=116

Now sub b=116 into [eqn 2] to find v
v=2(116)=232

So, b=116, and v=232

Answer 8

Here's a simple picture to see what's going on with the weighted average. The desired mix is 2/3 of the way from B to V, so you need more V to pull it closer. The relative distances tell you the relative amounts of each to include in the mix (1/3 and 2/3), and which one it's closer to tells you which one needs to be bigger (closer to V, so v is 2/3).