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Problem 14 - Entrance Test

A store sells two types of coffee beans: A and B. Bean A costs $12 per pound, and bean B costs $15 per pound. If a customer wants to create a blend of 10 pounds of coffee beans that costs $13.50 per pound, how many pounds of bean A should they use?

Correct: C

Let x be the number of pounds of bean A, and (10 - x) be the number of pounds of bean B. The total cost of the blend is 12x + 15(10 - x) = 13.50 * 10 = 135. 12x + 150 - 15x = 135 => -3x = -15 => x = 5.