Answer:
Approximately 55 years.
Step-by-step explanation:
Since, according to the rule of 72,
An amount is doubled when the product of time ( In years ) and the annual interest rate ( in percentage ) is 72.
Here, the annual rate of interest = 1.3 %,
Let after t years the economy will be doubled,
Thus, by the above rule,
[tex]1.3 t=72[/tex]
[tex]t=55.3846154\approx 55[/tex]
Thus, after 55 years ( approx ) the economy will be doubled.