Answer: 840 people
Explanation:
They surveyed 40 people in total and out of those 40, 21 said that sausage pizza was their favorite pizza.
The percentage of people who prefer sausage pizza is therefore:
= 21/40 * 100%
= 52.5 %
If there are 1,600 people in the festival and we assume that the sample is a representation of the people there, the estimated number of people who prefer sausage pizza will be:
= 52.5% * 1,600
= 840 people