(45 + 46 + 47 + .... + 113 + 114 + 115) is equal to

We can write , (45 + 46 + 47 + ....... + 114 + 115) = (1 + 2 + 3 +..... + 115) – (1 + 2 + 3 + .... + 44)

	∵ 1 + 2 + 3 + ..... + n =	n ( n + 1)
		2

Required answer =	115 × (115 + 1)	-	44 × (44 + 1)
	2		2

Required answer =	115 × 116	-	44 × 45
	2		2

Required answer = 115 × 58 – 22 × 45
Required answer = 6670 – 990 = 5680