diff --git a/calculator.js b/calculator.js
index caf34db..7d2dcab 100644
--- a/calculator.js
+++ b/calculator.js
@@ -11,5 +11,17 @@ function substract(num1, num2){
   return num1 - num2;
 }
 
+function multiple(num1, num2) {
+    return num1 * num2;
+}
+
+function divide(num1, num2) {
+    return num1 / num2;
+}
+
+
 module.exports.add = add;
 module.exports.isNumber = isNumber;
+module.exports.substract = substract;
+module.exports.multiple = multiple;
+module.exports.divide = divide;
\ No newline at end of file
diff --git a/index.html b/index.html
index cc6a9d9..d602a37 100644
--- a/index.html
+++ b/index.html
@@ -22,6 +22,8 @@ <h1>Silly Calculator</h1>
     <select id="operator" size="1">
       <option value="add">+</option>
       <option value="substract">-</option>
+	  <option value="multiple">*</option>
+	  <option value="divide">/</option>
     </select>
     <input type="text" id="num2" value="1" />
     <div>=</div>
diff --git a/main.js b/main.js
index 957a234..be82cd6 100644
--- a/main.js
+++ b/main.js
@@ -16,6 +16,12 @@ window.onload = function(){
     else if (operator == "substract"){
       document.getElementById('ans').value = substract(num1, num2);
     }
+    else if (operator == "multiple") {
+        document.getElementById('ans').value = multiple(num1, num2);
+    }
+    else if (operator == "divide") {
+        document.getElementById('ans').value = divide(num1, num2);
+    }
     else {
       alert("Bad operator!")
     }
diff --git a/test/test_calculator.js b/test/test_calculator.js
index 13f6205..b1fcb4a 100644
--- a/test/test_calculator.js
+++ b/test/test_calculator.js
@@ -6,5 +6,35 @@ describe('Calculator', function(){
     it('add', function(){
       assert.equal('2', cal.add(1, 1));
     })
+    it('add negative', function () {
+        assert.equal('-2', cal.add(-1, -1));
+    })
+  })
+
+  describe('substract', function () {
+      it('substract', function () {
+          assert.equal('5', cal.substract(10, 5));
+      })
+      it('substract negative', function () {
+          assert.equal('-5', cal.substract(-10, -5));
+      })
+  })
+
+  describe('multiple', function () {
+      it('multiple', function () {
+          assert.equal('50', cal.multiple(10, 5));
+      })
+      it('multiple negative', function () {
+          assert.equal('50', cal.multiple(-10, -5));
+      })
+  })
+
+  describe('divide', function () {
+      it('divide', function () {
+          assert.equal('2', cal.divide(10, 5));
+      })
+      it('divide negative', function () {
+          assert.equal('2', cal.divide(-10, -5));
+      })
   })
 })