Guess and Check #15

GC #15

GC #15 hints and answers

A stock market analyst sold a monthly newsletter to 500 subscribers at a price of $ 10 each. She discovered that for each $0.25 increase in the monthly price of the newsletter, she would lose 2 subscriptions. For what price should she sell each issue to bring in the greatest total monthly income?

  • This is a type of problem that students often encounter in calculus classes! But we can solve it by applying a little common sense, a little patience, and (if we want to prove that our answer is correct) a little algebra.
  • First, let's make sure we understand what is going on in the problem. At first our analyst is selling 500 newsletters at $10 each, for an income of $5,000.
  • Now suppose she increases the price of the newsletter to $11. According to the problem, she would then lose 8 subscribers. So she'll only sell 492 newsletters. But her income will now be $11 x 492 = $5,412.
  • Of course, she can't increase the price too much, or no one will buy it, and she won't make any money.
  • You can try various prices to figure out for what price her monthly income is as big as possible.

As always, be sure to explain the work you did to arrive at your answers!