# Project Euler problem one

• February 3rd, 2013, 08:48 AM
lanmonster
Project Euler problem one
I am using Project Euler to test myself on the Java programming that I am teaching myself and here is problem one: 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.

Here is my Java attempt at calculating it
Code :

```public class problemOne { public static void main(String[] args) { int count; int sum = 0; //Multiples of 3 for(count = 0; count < 1000; count += 3){ System.out.println("count is: " + count); sum = sum + count; } //Multiples of 5 for(count = 0; count < 1000; count += 5){ System.out.println("count is: " + count); sum = sum + count; } System.out.println("Total is: " + sum); } }```
I get 26333 as the answer but when I enter that at projecteuler.net it says incorrect.
Is there an error in the logic that I used to calculate? If so, where is it so I can rethink it.
• February 3rd, 2013, 09:01 AM
curmudgeon
Re: Project Euler problem one
You're forgetting that some numbers are multiples of *both* 3 and 5, and you are in effect adding these numbers *twice*.
• February 3rd, 2013, 09:47 AM
lanmonster
Re: Project Euler problem one
Quote:

Originally Posted by curmudgeon
You're forgetting that some numbers are multiples of *both* 3 and 5, and you are in effect adding these numbers *twice*.

Thanks
• February 3rd, 2013, 04:10 PM
lanmonster
Re: Project Euler problem one
I got it figured out! Now on to problem 2...