SOLUTION: This is a substitution/elimination problem. A coffee counter charges 9.00 per pound for Kenyan French Roast coffee and 8.00 per pound for Sumatran coffee. How much of each type sho

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Question 442915: This is a substitution/elimination problem. A coffee counter charges 9.00 per pound for Kenyan French Roast coffee and 8.00 per pound for Sumatran coffee. How much of each type should be used to make a 20 pound blend that sells for 8.40 a pound?
Answer by nerdybill(7384) About Me  (Show Source):
You can put this solution on YOUR website!
A coffee counter charges 9.00 per pound for Kenyan French Roast coffee and 8.00 per pound for Sumatran coffee. How much of each type should be used to make a 20 pound blend that sells for 8.40 a pound?
Let x = amount(lbs) of kenyan coffee
and y = amount(lbs) of Sumatra coffee
.
x+y = 20 (equation 1)
.
9x + 8y = 8.40(20) (equation 2)
.
solve equation 1 for y:
y = 20-x
substitute into equation 2:
9x + 8(20-x) = 8.40(20)
9x + 160-8x = 168
x + 160 = 168
x = 8 pounds (Kenyan)
.
Sumatra:
x+y = 20
8+y = 20
y = 12 pounds