pe0001.mathematica

(*
1) 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.
*)

Total[Select[Range[999], Mod[#, 3] == 0 || Mod[#, 5] == 0 &]]