sanju09 wrote:How many pounds of coffee that costs $4.00 per pound need to be mixed with 10 pounds of coffee that costs $6.40 per pound to create a mixture of coffee that costs $5.50 per pound?
(A) 4
(B) 6
(C) 8
(D) 10
(E) 16
This is a weighted average problem.
Ignoring the decimals:
$400 coffee is being combined with $640 coffee to form a mixture of $550 coffee.
We can use alligation:
The proportion needed of each type of coffee is equal to the positive difference between the OTHER two prices.
Proportion needed of $400 coffee = |640-550| = 90.
Proportion needed of $640 coffee = |400-550| = 150.
Required ratio:
$400 coffee : $640 coffee = 90:150 = 3:5.
Since the mixture is to contain 10 pounds of the $640 coffee, and 3:5 = 6:10, 6 pounds of the $400 coffee are needed.
The correct answer is
B.
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