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Question from Iona, a student:

I borrowed $6000. 00 from  a friend to pay school fee. He said I should not pay back any interest but pay $350.00 monthly after graduation.
(1) Make an equation from the above
(2) make a graph
(3) what is the relationship between the months after graduation and the loan?
(4) what is the horizontal and vertical intercept relate to the problem?

Hello Iona.

I can get you started on this problem. Think of time (the number of months after graduation) as the horizontal axis and debt (the loan balance) as the vertical axis. If M is the number of months and B is the balance owing then there are several things we can say in order to come up with the equation.

  1. When M = 0 (time of graduation), the balance owing is $6000.
  2. For every M, the balance goes down by $350.

So B starts at $6000, but you subtract $350 for every M. That means you subtract M times $350. So

B = 6000 - 350M.

Now graph this relationship. If it helps you sort things out, you can replace it with

y = -350x + 6000.

which is the same thing if y is the balance owing and x is the number of months since graduation.

Look at the graph carefully and you'll be able to answer parts (3) and (4).

Hope this helps,
Stephen La Rocque.

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