Answer
Total saving for the first 30 day = 1,073,741,824
Work Step by Step
Given
The saving on first day $x_{1}$ = 1
As saving doubles next day (common ratio)(r) = 2
Total saving given by summation formula $S_{n}$ = $\frac{a(1 - r^{n})}{1 - r}$
Total saving for the first 30 day = $S_{30}$ = $\frac{1(1 - 2^{30})}{1 - 2}$ = $\frac{(1 - 1073741824)}{1 - 2}$ = $\frac{-1073741823}{-1}$ = 1073741823
