Question

the sum of all the natural numbers from 50 to 100 are

Answer 1

Here the series is 50,51,52,..., 100.
So a=50; d= 1 and n= 100-50+1=51
$$\begin{gathered} Sum=\frac{n}{2}(2a+(n-1\left)d\right) \\ =\frac{51}{2}\left(2\right(50)+(51-1\left)1\right) \\ =\frac{51}{2}(100+50) \\ =51*75 \\ =3825 \end{gathered}$$