Suchita,
Here suppose 1 cut is made, we will have two pieces.
Now suppose the 2nd cut is made parallel to the first cut on the pizza, then we will have only 3 pieces after 2 cuts.
But say suppose we make two cuts, such that the two cuts pass through the centre then we will have 4 pieces. So we can see that the maximum number of pieces can only be obtained when the next cut made intersect the other cuts made.
Now that the third cut must intersect the previous two cuts made, not at the point of intersection of the 1st two cuts, but in two points that distinctly.
ie the third cut must intersect the 1st and the 2nd cut at two different points, so that the maximum number of pieces is obtained.
So that after the 3rd cut we can have a maximum of 7 pieces.
And keep proceeding in that manner.
Hope it helps.
Regards,
Ashwin (IIT MadraS).