$\"\"$

Consider Principal income is $\"\"$ .

The total investment is compunded annually and doubled in three years.

Therefore,the total investment is $\"\"$ .

Time period is $\"\"$ years.

Find the rate of interest .

Compound interest formula: $\"\"$ .

For annually compounded $\"\"$ .

Substitute the corresponding values in the formula.

$\"\"$

Therefore,the rate of interest is $\"\"$ .

$\"\"$

The rate of interest is $\"\"$ .