diff --git a/sum.js b/sum.js
index 3b973dc..5821c94 100644
--- a/sum.js
+++ b/sum.js
@@ -3,4 +3,13 @@ function sum(a, b) {
   return a + b;
   
 }
+
+function sub(a, b) {
+  return a - b;
+}
+
+function prod(a, b) {
+  return a * b;
+}
+
 module.exports = sum;