on the last question from my maths text book and i've gotten all previous questions right but this last one.
25. Jenny puts aside $20 at the end of each month for 3 years. How much will she have at the end of the 3 years if the investment earns 8.2% p.a., paid monthly?
(p.a. means per annum so yearly)
answer is : $813.16
btw this chapter is based on using the sum of a geometric series formula.
so ive been using this formula
Sn = a[(r^n) - 1]
aaaaaaar - 1
a: being the first amount in the geometric series
r: being the ratio or interest rate
n: being the no. of years or the time period.
unless theres another formula or way of figuring this out because i keep stuffing up something in my working out.
thx all help appreciated.