There's a mistake in your posting - the large pizza cannot have a diameter of 1 inch. Nonetheless, area is fairly easy to compute once you know the formula. I will try to explain the formula & how to use it, then leave it to you to compute the area of the large pizza. You will simply subtract the area of the small pizza from the area of the large one & that result will represent how much more pizza you get with the large size.
First, we assume that we're considering round pizzas - not square or rectangular ones. Computing the area of a round pizza uses the formula for area of a circle: πr2
That is pi x radius x radius. As radius is half of diameter, you divide the diameter by 2 & square the result - or multiply it times itself. Finally, you multiply that result by the value of pi (3.14159...). You might have a calculator with that value stored in one of the keys, or you might round it off to 3.142 or 3.1416.
In the case of your small pizza, the diameter being 10 inches, it will have a radius of 5:
25 x pi = 78.54 square inches
Use the same procedure to find the area of the large pizza, then subtract 78.54 sq.in. That's all there is to it.
I hope this helps you. Good luck!