Published on Friday, 5th October 2001, 06:00 pm; Solved by 1009580; Difficulty rating: 5% 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 $1000$.