# The Clock

###### Teacher's Guide

In this short guide you will be able to preview the segment. You’ll also get some great ideas for in-class activities after watching the video with your students.

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## G U A R A N T E E !

This activity will show your students the beauty of math and patterns. ### Introduction

Tell your students that you can predict if a number divided by 3 will have a remainder or not, without a calculator!

### What to do Ask a volunteer to write a zip code on the blackboard. Before the volunteer finishes writing the number you will announce if it can be divided by 3 with or without a remainder. If the number has a remainder, you can ask the volunteer to add another digit so that the new number can be divided by 3 with no remainder. Ask your students to check on their calculators to see if you were correct. Let them practice this Math-Magic game working in pairs. It’s a great way to sharpen their mental math in a fun way! ## How it Works

✅ Let’s say the volunteer wrote 21657. ✅ When you are adding the digits, you get the sum of 21 which is divisible by 3 with no remainder. If you can divide the sum of the digits by 3 with no remainder, the original number (21657) can also be divided by 3 with no remainder. ✅ And here is something even more exciting – mix the order of the digits and you will see that all the combinations will divide by 3 with no remainder as well! ✅ Now, in case your volunteer chooses, for example, the number 75122, when you add the digits and get 17, you know that there is a remainder when you divide that number by 3. Since 18 divides by 3, and 17 is one digit short you can offer to add 1 to the number to obtain 751221. This new number is now divisible by 3 with no remainder!

Isn’t that awesome?! ### Watch Video

After watching the Study Guide
it is time to share “The Clock”

🔹 Please note: you must have a