Problem:

 

Janet has $140 and she adds $50 to her savings at the end of each month.  She asks three of her friends when she will have $1000. Their work is shown below.

Explain how each method is alike and how each will give a correct solution.

 

 

Ann:         y = 140 + 50x              

 

           1000 = 140 + 50x

  1000 - 140 = 140 – 140 + 50x

        860/50 = 50x/50

            17.2 = x

                       

Mark:

           

Months	0	1	2	4	8	12	16	18
Profit $	140	190	240	340	540	740	940	1040