Why is it important to use real rather than nominal gdp figures when making comparisons of output across time periods?

The real GDP figures reflect changes in the quantity of output and not the changes in the general level of price.

Explanation:

The nominal GDP is the total values of all the goods and the services produced in a given time period and are expressed as usually in the quarterly and annually. The real is the nominal and os adjusted to the inflation and the real GDP measure the actual growth without destroying the effects form the inflation.