Question

Find the sum of all even numbers between 21 to 150.

• A. 4500
• B. 5090
• C. 5590
• D. 6150

Answer 1

The correct option is C 5590

Sum of even numbers between 21 to 150 =
Sum of all even numbers till 150 - sum of all even numbers till 20
= (2+4+6+8......150) - (2+4+6+8...20)
= 2 (1+2+3+4......75) - 2 (1+2+3+4...10)
Sum of first n terms = $\frac{n(n+1)}{2}$
= 2 x 75 x 76 - 2 x 10 x 11
2 2
= 75 x 76 - 10 x 11
= 5590