equation...

ganonbanned · Post by **ganonbanned** » Sat May 12, 2007 1:52 pm

hey, does anyone know how to do this problem?

peanuts sell for $3 per pound. cashews sell for $6 per pound. How many cashews should be mixed with 12 lbs. of peanuts to obtain a mixture that sells for $4.20 per pound?

timmeh87 · Post by **timmeh87** » Sat May 12, 2007 2:11 pm

let p be the mass of peanuts, and c be the mass of cashews. the price per pound of an arbitraty mixture is then

Code: Select all

3p + 6c
--------   = price per pound
p + c

which is the total price over the total weight.

the question gives p and $/lb, so solve for c.

no i wont do it for you.

Zzebotes13 · Post by **Zzebotes13** » Sat May 12, 2007 2:14 pm

I did these in school like 4 months ago. I think u do it like this:

3x + 6y= 4.20
x + 12y= 4.20
- then u use linear combinations

x= cashews, y= peanuts

the answer i believe to be x=$0.84

ganonbanned · Post by **ganonbanned** » Sat May 12, 2007 2:14 pm

Thanks.

thats ok that you dont do it for me, I need to show work anyway.

timmeh87 · Post by **timmeh87** » Sun May 13, 2007 10:47 am

Zzebotes13: you answered in $ but the question wanted pounds?

Zzebotes13 · Post by **Zzebotes13** » Sun May 13, 2007 3:35 pm

sorry, i didn't read the full question.

Kurt_ · Post by **Kurt_** » Sun May 13, 2007 4:09 pm

peanuts sell for $3 per pound. cashews sell for $6 per pound. How many cashews should be mixed with 12 lbs. of peanuts to obtain a mixture that sells for $4.20 per pound?

I would do it like this:

Let p be the weight of peanuts in lbs.
Let c " " " "lbs.

12lbs. = amount of peanuts in the mixture.
(3p + 6c) / total weight = 4.20

3(12) + 6c / total weight = 4.20

36 + 6c / 12+c = 4.20

36 + 6c = 4.20(12) + 4.20c
36 - 4.20(12) = 4.20c - 6c

-14.4 = -1.8c
c = 14.4/1.8
c = 8

8 pounds of cashews.

Nothing hard at all. It's an isolating for c question.

(Now that I look at it, Tim had it right too. Only I did it!)