Question

What is the sum of all even integers greater than 100 and less than 1000?

Answer 1

Formula is : an = a1 + ( n-1) d

starting (a1) = 101 , ending (an = 999)

999 = 101 + (n-1)

n = 450

formula is : s = ( n /2 ) ( a1 + an )

= (450/2) (101 + 999)

Explanation: