Question

the sum of even numbers between 1 and 31 is

Answer 1

The answer is 260 but the solution i have not done

Answer 2

Answer:

Even numbers : 2,4,6..........30

a =2 d=4-2=2

An =a +(n-1)d

30=2 +(n-1)2

30-2=(n-1)2

28/2=n-1

14=n-1

n=14+1

n= 15

Sn =n/2[2a +(n-1)d]

=15/2[2(2)+(15-1)2]

=15/2[4+(14)2]

=15/2[4+28]

= 15/2*32

=15*16

=240