Fiscal deficit was 4% of the GDP in 2015 and that increased to 5% in 2016. If the GDP increased by 10% from 2015 to 2016, the percentage increase in the actual fiscal deficit is ____________.

The correct option is 37.50.

Let us understand the step-by-step derivation to find the percentage increase in the actual fiscal deficit from 2015 to 2016.

Step 1: Define the variables for GDP
Let the Gross Domestic Product (GDP) in the year 2015 be represented as:
$${\mathrm{GDP}}_{2015}=X$$
According to the problem, the GDP increased by 10% from 2015 to 2016. Therefore, the GDP in the year 2016 is:
$${\mathrm{GDP}}_{2016}=X+0.10X=1.10X$$

Step 2: Calculate the actual fiscal deficit for both years
In 2015, the fiscal deficit was 4% of the GDP. Thus, the actual fiscal deficit in 2015 (${\mathrm{FD}}_{2015}$) is:
$${\mathrm{FD}}_{2015}=4\%of{\mathrm{GDP}}_{2015}=0.04X$$
In 2016, the fiscal deficit increased to 5% of the GDP. Thus, the actual fiscal deficit in 2016 (${\mathrm{FD}}_{2016}$) is:
$${\mathrm{FD}}_{2016}=5\%of{\mathrm{GDP}}_{2016}=0.05\times 1.10X=0.055X$$

Step 3: Calculate the percentage increase in the actual fiscal deficit
The increase in the actual fiscal deficit is the difference between the actual deficit in 2016 and 2015:
$$Increase={\mathrm{FD}}_{2016}-{\mathrm{FD}}_{2015}=0.055X-0.04X=0.015X$$
Now, the percentage increase is calculated relative to the initial fiscal deficit in 2015:
$$Percentage\; Increase=\left(\frac{0.015X}{0.04X}\right)\times 100$$
Simplifying the expression by dividing the coefficients:
$$Percentage\; Increase=\frac{15}{40}\times 100=\frac{3}{8}\times 100=37.50\%$$
Hence, the percentage increase in the actual fiscal deficit is 37.50.