diff --git a/index.js b/index.js
index 80d3cb399d69500993779430df426548ac16365d..e3053f8cd559b38bbba4c2251f49eaa402895dcf 100644
--- a/index.js
+++ b/index.js
@@ -6,7 +6,15 @@ function subNumbers(a, b) {
   return addNumbers(a, -b);
 }
 
+function mulNumbers(a, b) {
+  let acc = 0;
+  for (let i = 0; i < b; i++)
+    acc = addNumbers(acc, a);
+  return acc;
+}
+
 module.exports = {
   addNumbers,
   subNumbers,
+  mulNumbers,
 }
diff --git a/index.test.js b/index.test.js
index e230d9f8219ed1bd5921b8ef2bd209fbf6a9a54f..6abbf0a80574e6d667e3d3a4753f42aee066b88b 100644
--- a/index.test.js
+++ b/index.test.js
@@ -1,9 +1,8 @@
-const { addNumbers, subNumbers } = require('./index');
+const { addNumbers, subNumbers, mulNumbers } = require('./index');
 
 test('adds 1 + 2 to equal 3', () => {
   expect(addNumbers(1, 2)).toBe(3);
 });
-
 test('adds -1 + 2 to equal 1', () => {
   expect(addNumbers(-1, 2)).toBe(1);
 });
@@ -11,7 +10,13 @@ test('adds -1 + 2 to equal 1', () => {
 test('subs 1 - 2 to equal -1', () => {
   expect(subNumbers(1, 2)).toBe(-1);
 });
-
 test('subs -1 - 2 to equal -3', () => {
   expect(subNumbers(-1, 2)).toBe(-3);
 });
+
+test('muls 1 * 2 to equal 2', () => {
+  expect(mulNumbers(1, 2)).toBe(2);
+});
+test('muls -1 * 2 to equal -2', () => {
+  expect(mulNumbers(-1, 2)).toBe(-2);
+});