Question

A merchant has coffee worth $20 a pound that she wishes to mix with 30 pounds of coffee with $60 a pound to get a mixture that is worth $30 a pound. How many pounds of the $20 coffee should be used?

Answer 1

90 pounds

Explanation:

Let x represent the number of pounds of $20 coffee in the mix. Then the cost of the mix is ...

20x + 60·30 = 30(30+x)

20x + 1800 = 900 +30x . . . . . eliminate parentheses

900 = 10x . . . . . . . . . . . . . . . . . subtract 900+20x

90 = x . . . . . . . . . . . . . . . . . . . . divide by 10

90 pounds of $20 coffee should be used.