   SEARCH HOME Math Central Quandaries & Queries  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.     Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.