The GDP deflator can be calculated using the following formula:
\[ \text{GDP deflator} = \left( \frac{\text{Nominal GDP}}{\text{Real GDP}} \right) \times 100 \]
Plugging in the given values:
\[ \text{GDP deflator} = \left( \frac{5500}{5000} \right) \times 100 = 1.1 \times 100 = 110 \]
Therefore, the GDP deflator is 110.