Originally Posted by
CaptainBlack Let the original sum be x
The sum after $\displaystyle 1$ year is $\displaystyle 1.06 \times x$
After $\displaystyle 2$ years $\displaystyle 1.06 \times (1.06 \times x)=1.06^2 ~x$
After $\displaystyle 3$ years $\displaystyle 1.06 \times (1.06^2 ~ x)=1.06^3 ~x$
After $\displaystyle N$ years $\displaystyle 1.06 \times (1.06^{n-1} ~ x)=1.06^N ~x$
So the fund has $\displaystyle 1.06^{18} ~x=17000$ on the girls 18th birthday, now solve for $\displaystyle x$.
(This is an initial sum of $\displaystyle x$ compounded annulaly for 18 years at a rate of 6%)
RonL