All solutions here are SUGGESTED. Mr. Teng will hold no liability for any errors. Comments are entirely personal opinions.

(i)

Using the graphing calculator, smallest n = 24.

Thus, Mrs A’s account will have more than latex = 100 \times 1.005latex = (100 \times 1.005 + 100) \times 1.005 = 100 \times 1.005^2 + 100 \times 1.005latex = 100 \times 1.005^n + \ldots 100 \times 1.005latex = 20100 (1.005^n – 1)5000 on September 2004.

(iii)

Using Graphing Calculator,

Thus the interest rate is 1.80% per month.

### KS Comments:

Students should reproduce the table (with its succeeding and preceding values) to substantiate their answers for (i) and (ii). For (i), its necessary to identify the month; just use your fingers to count.