The sum of series, (–100) + (–95) + (–90) + …

• Progressions

The sum of series, (–100) + (–95) + (–90) + …………+ 110 + 115 + 120, is:

1. 0
2. 220
3. 340
4. 450
5. None of the above

Answer

First Term = -100

Last Term = 120

Number of Terms = 45

Sum = ½n(a + l) = 45(120 - 100)/2 = 450

Another way to solve: negative and positive terms till 100 will cancel each other.

So, sum = 105 + 110 + 115 + 120 = 450

The correct option is D.