Question 158245
It says the cost varies inversely with the number of notebooks. That means that as the number of books increases, the cost per book decreases. That's your first clue that your answer is wrong. You set up a direct proportion, y=kx, rather than an inverse proportion, y=k/x. Since the cost is $.50 per book for 10,000 books, you can write the equation .50 = k/10000, so k = 5000. That means the inverse function is y = 5000/x. Now substitute 18000 for x to get y = 5000/18000 = 0.27777. So it costs 28 cents per notebook when 18,000 are manufactured.