Question

Colortime bakers wants to make 30 pounds of a berry mix that costs $3 per pound to use in their pancake mix. they are using blueberries that cost $2 per pound and blackberries that cost $3.50 per pound. how many pounds of blackberries should be used in this mixture?

Answer 1

We know that the total cost will be 30 lb * $3/lb = $90. We can thus set up an equation such that: 90 = 3.5*b + 2*(30-b), where b is the weight of blackberries and 30-b represents that which is not blackberries, that is, the blueberries.   
We solve the equation as: 
 90 = 3.5b +60 -2b = 1.5b + 60
 30 = 1.5b
 b = 20
  Thus 20 lbs of blackberries (and 10 lbs of blueberries) are needed.