Answer
Total saving for the first 15 day = 32767
Work Step by Step
Given
The saving on first day $x_{1}$ = 1
As saving doubles next day (common ratio)(r) = 2
Total saving for the first 15 day given by summation formula $S_{n}$ = $\frac{a(1 - r^{n})}{1 - r}$
$S_{15}$ = $\frac{1(1 - 2^{15})}{1 - 2}$ = $\frac{(1 - 32768)}{1 - 2}$ = $\frac{-32767}{-1}$ = 32767
