So many slices!

So, this is how Jesus fed the 5,000 as mentioned in the bible, Matthew 14:13-21.

Note that to divide the pizzas into maximum peices we should cut its lines in such a way that no two are parallel and no three are concurrent.
Now, using one slice we can make a maximum of $2$ parts.
Now, using two slices we can make a maximum of $4$ parts.
Now, using three slices we can make a maximum of $7$ parts.
Now, using four slices we can make a maximum of $11$ parts.
Now, using five slices we can make a maximum of $16$ parts.

So, we see that using $n$ slices we can make a maximum of $1 + \displaystyle\sum_{i=1}^{n} i$
So using 100 slices we can make a maximum of $1 + \displaystyle\sum_{i=1}^{100} i = 1 + \dfrac{100 × 101}{2} = \color{#3D99F6}{\boxed{5051}}$

---

An alternative method is to realize that with every slice we are cutting the existing parts into a maximum of $n$ more parts. Eg:- If in slice 5 we make 16 parts, in slice 6 we cut in such a way that in passes through 4 points thus making 5 more pieces than first, which leads to the same result as above.

I used the formula n(n+1)/2 + 1...

We can use the derived formula $f(n)=\dfrac{1}{2}(n^2+n+2)$ . We have

$f(100)=\dfrac{1}{2}(100^2+100+2)=\boxed{5051}$

I saw this problem before in a PDF called concrete mathematics