Answer
The saving on thirtieth day $x_{30}$ = 536870912
Work Step by Step
Given
Saving on first day $x_{1}$ = 1
As saving will be twice next day (common ratio)(r) = 2
By formula $x_{n}$= $x_{1} r^{n-1}$
The saving on thirtieth day $x_{30}$ = $1\times(2)^{30 - 1}$ = $(2)^{29}$= 536870912