This is a rolling update post for responses to this morning's post.

The Admirable **Adam Atkinson** has emailed to suggest an answer I hadn't considered: **100**.

"I could imagine many programming languages would say 100. You start with the first term, 100. discover that the "next" number, 101, is outside your range of summation, and stop there. I don't know that I'm saying this would be my answer but I could imagine some people supporting it."

I agree, it would be perfectly possible for a computer language to interpret this as something like:

total = 0

count = 100

do

total += count

count += 1

until count >= 0

... although I don't know any languages off the top of my head that would do that. Adam notes that Perl considers the sum to be 0.

## Colin

Colin is a Weymouth maths tutor, author of several Maths For Dummies books and A-level maths guides. He started Flying Colours Maths in 2008.
He lives with an espresso pot and nothing to prove.