Project Euler Forum

)If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.

Find the sum of all the multiples of 3 or 5 below 1000.)
Wouldn't the true answer to this question would be negative infinity because 0 isn't indicated to be the stopping point?

It says natural numbers, and that means that negative numbers are not included. Conventions differ on whether 0 is a natural number or not (it usually is not considered natural), but that does not matter here since it has no influence on the answer.

http://en.wikipedia.org/wiki/Natural_number

Encountering these instructions: "Find the sum of all the multiples of 3 or 5 below infinity." If I constrain the problem to natural numbers, the answer obviously diverges. I am able to see the numeric pattern, and could express it if I had guidelines for doing so within the dialog box for the answer. Of course, if we allow ALL multiples of 3 or 5 below a finite number, well, they could include all the negative multiples as well. But the problem starts with an example of natural numbers. I think we need more context to answer this question, or at least some guidelines for expressing an answer, which currently does not lend itself to a simple numeric figure. I would love to answer this question and believe I know how - if the question (or the expected response) could be clarified I would be happy to continue with it!

drjamesneiman wrote: Tue Sep 02, 2025 4:56 pm Encountering these instructions: "Find the sum of all the multiples of 3 or 5 below infinity."

I don't understand. Where do you encounter these instructions? I've never seen them, but then I don't know all the Project Euler problems.

drjamesneiman is talking about bonus problem #1

The answer can be written exactly. Any further comments on how to give your answer might be considered a spoiler. Though if you have the correct answer, there shouldn't be much ambiguity on how to write the answer

byhill wrote: Tue Sep 02, 2025 8:04 pm drjamesneiman is talking about bonus problem #1

The answer can be written exactly. Any further comments on how to give your answer might be considered a spoiler.

I had come to the conclusion that the question is a troll rather than a mathematical problem.