diff --git a/sum-of-multiples.md b/sum-of-multiples.md
index 07d99e3ac0..f55cdeb394 100644
--- a/sum-of-multiples.md
+++ b/sum-of-multiples.md
@@ -1,7 +1,7 @@
-If we list all the natural numbers up to but not including 15 that are
-multiples of either 3 or 5, we get 3, 5, 6 and 9, 10, and 12.
+If we list all the natural numbers up to but not including 20 that are
+multiples of either 3 or 5, we get 3, 5, 6 and 9, 10, 12, 15, and 18.
 
-The sum of these multiples is 45.
+The sum of these multiples is 78.
 
 Write a program that can find the sum of the multiples of a given set of
-numbers.
+numbers. If no set of numbers is given, default to 3 and 5.