(51 + 52 + 53 + … + 100) = ?

Question:
(51 + 52 + 53 + … + 100) = ?

[A].

2525

[B].

2975

[C].

3225

[D].

3775

Answer: Option D

Explanation:

Sn = (1 + 2 + 3 + … + 50 + 51 + 52 + … + 100) – (1 + 2 + 3 + … + 50)

=	100	x (1 + 100) –	50	x (1 + 50)
	2		2

    = (50 x 101) – (25 x 51)

    = (5050 – 1275)

    = 3775.