Question

Find the sum of 50 terms of ap 2,4,6,8,

Answer 1

$a = 2 \: \\ d \: = 4 - 2 = 6 - 4 = 8 - 6 = 2 \\sn \: = \frac{n}{2} (2a + nd - d) \\ s50 = \frac{50}{2} (4 + 98) \\ 25(102) \\ 2550$

Answer 2

Given :

Ap : 2,4,6,8,...

To Find :

Find the sum of 50 terms

Solution:

Ap : 2,4,6,8,...

First term = a = 2

Common difference = d = 4-2=6-4=2

Formula of sum of first n terms = $S_n=\frac{n}{2}(2a+(n-1)d)$

Substitute n = 50

$S_{50}=\frac{50}{2}(2(2)+(50-1)(2))\\ S_{50}=2550$

Hence  the sum of 50 terms of ap is 2550