**Calculation of Simple Interest**

To find the amount, we need to calculate the simple interest first. The formula to calculate simple interest is:

Simple Interest = (Principal * Rate * Time) / 100

Here,
Principal = 1425
Rate = 4%
Time = 3 years 3 months

**Converting Time into Years**

To calculate the time in years, we need to convert 3 years 3 months into a decimal form.

3 years = 3
3 months = (3/12) = 0.25

Total Time = 3 + 0.25 = 3.25 years

**Calculating Simple Interest**

Now, let's calculate the simple interest using the given values:

Simple Interest = (1425 * 4 * 3.25) / 100

Simple Interest = 185.25

**Calculating Amount**

The amount can be calculated by adding the principal to the simple interest:

Amount = Principal + Simple Interest

Amount = 1425 + 185.25

Amount = 1610.25

Therefore, the amount after 3 years 3 months at a simple interest rate of 4% per annum is 1610.25.

In this calculation, we have used the formula for simple interest and converted the given time into years to calculate the interest accurately. The final amount is obtained by adding the principal to the calculated simple interest.