Question 1195566
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The other two responses you have received show formal algebraic solutions.<br>
If formal algebra is not required, you can solve this using logical reasoning and simple calculations.  And doing that will give you good mental exercise.<br>
The number of pounds of coffee of type B is twice the number of pounds of coffee of type A.  So the cost of each 3 pounds of coffee is 2($5.70)+1($4.60)=$16; that makes the cost per pound of the mixture $16/3.<br>
The total cost was $640, so the number of pounds of mixture was<br>
{{{640/(16/3)=640(3/16)=3*40=120}}}<br>
Since the mixture was 120 pounds, 40 pounds were type A coffee and 80 pounds were type B coffee.<br>
ANSWER: 40 pounds of type A coffee were used<br>