Posted by CrissyXD on .
(COMPOUND INTEREST)
Effie is planning to set up a trust fund for her new grand daughter. In 18 years time she wants the investment to be worth $50000 to help her buy a car or a home unit.
a)How much should she invest at 5% p.a. compounding yearly?
I know the answer for this is $20776.03
b) How much less will she have to invest at 6% p.a., compounding monthly?
This is the question I need help with...
Does anyone know the working out and answer? thank you

Math 
Reiny,
let her present investment be P
P(1.05)^18 = 50000
P = 50000/(1.05)^18 = 20776.03
for the 2nd part,
monthly rate = .06/12 = .005, but the exponent = 12x18 = 216
P = 50000/1.005^216 = 17025.53