Have coffee that is $7/lbs, have 14lbs of coffee that is $4/lbs. Need mixture for $5/ lbs.?

Question

Have coffe that is $7/lbs, have 14lbs of coffe that is $4/lbs. Need mixture for $5/ lbs.
Please help. how do i solve this?

M3 · Accepted Answer

use minimum variables !
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let x lbs of coffee @ $7/lb be added, then

7x + 4*14 = 5(x+14)

7x - 5x = 14(5 - 4)

2x = 14

x = 7 lbs 
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Ralph 124c41 · Answer

Let
P(1) =  price of coffee 1
W(1) =  weight of coffee 1
P(2) =  price of coffee 2
W(2) =  weight of coffee 2
Then the formula for the value of the mix would be the value of each component divided by the total weight
P = (P(1)W(1)+P(2)W(2))/(W(1)+W(2)
Assume you need to use all 14 lbs of $4 coffee
5 = (7W(1)+4×14)/(W(1)+14)
5(W(1)+14) = (7W(1)+4×14)
5W(1)+70 = 7W(1)+56
2W(1) = 14
W(1) = 7

Have coffee that is $7/lbs, have 14lbs of coffee that is $4/lbs. Need mixture for $5/ lbs.?

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