# Making Division Fun: A Masterclass in Teaching Divisibility by 7

Divisibility rules are foundational building blocks of elementary math, acting as gateways to more complex operations, such as simplifying fractions or factoring large numbers. Often, students find these rules abstract and challenging to grasp, especially when it comes to understanding the rule for divisibility by 7. Today, we’ll break this barrier down and transform learning into a fun, engaging activity that will not only cement the concept in the students’ minds but will also enhance their mathematical prowess. Let’s unravel the activity, “Divisibility by 7: Make it Count!”

## Unpacking the Divisibility by 7 Rule

Before jumping into the activity, it’s critical to ensure that the concept is clear. A number is divisible by 7 if, when we triple the last digit and add it to the remaining number, the result is divisible by 7. This technique might not sound very intuitive, but with regular practice, students will find it a handy shortcut. Let’s illustrate this rule with some examples:

Example 1: Consider the number 42. Here, applying our rule, we triple the last digit (2) and add it to the number formed by the remaining digit(s) (4). So, we have 3(2) + 4 = 6 + 4 = 10, which isn’t divisible by 7. We need to repeat the process. So, 3(0) + 1 = 1, which is not divisible by 7. This means 42, despite being a multiple of 7, doesn’t work with this rule.

However, the rule does hold in many instances:

Example 2: Consider 329. Applying the rule, we have 3(9) + 32 = 27 + 32 = 59. Now, 59 is not divisible by 7, so we apply the rule again: 3(9) + 5 = 27 + 5 = 32. Not divisible by 7 yet again, but applying the rule one more time gives us 3(2) + 3 = 6 + 3 = 9, which is not divisible by 7. Therefore, 329 is not divisible by 7.

These exercises show the rule is not foolproof. It’s not universally applicable, which can add to its complexity.

## Let’s Get the Ball Rolling: The Activity

Now, let’s transform this seemingly dull concept into an exhilarating math game that students will love to play. The aim of the game is to encourage students to practice the divisibility rule for 7 and gain fluency. Moreover, this game will stimulate mathematical thinking and reasoning as students will strive to create numbers that are divisible by 7. Here’s how to play:

1. Pair Up: Have each student pick a partner. This game encourages cooperative learning, promoting social skills alongside mathematical skills.
2. Turn-Based Gameplay: In their pairs, Partner A will create a three-digit number for Partner B to analyze. Partner B will apply the divisibility rule to determine if the number is divisible by 7 or not. After recording each other’s answers, Partner B will create a number for Partner A, and the cycle continues.
3. The Time Factor: Set a timer for 25 minutes. The time constraint adds a layer of excitement to the activity and encourages quick thinking.
4. Goal Setting: Ensure that you state the goal of the game before the students begin. The pair that reports the most numbers divisible by 7 at the end of the game wins!

Example of Gameplay: Suppose we have Partner A and Partner B. Partner A starts by providing the number 777. Partner B applies the divisibility rule: 3(7) + 77 = 21 + 77 = 98. Applying the rule again, 3(8) + 9 = 24 + 9 = 33, which is not divisible by 7. Therefore, 777 is not divisible by 7.

## The Importance of Accommodations and Modifications

Accommodations and modifications are essential to ensure that all students can participate in the activity fully.

Accommodations: For students who may struggle with this activity, consider allowing them to use a multiplication chart or calculator during gameplay. This accommodation will enable them to participate actively without getting bogged down by calculations they find difficult.

Modifications: For students who find this activity too easy or need an extra challenge, you might modify the game by adding extra conditions. For example, you might stipulate that the three-digit numbers must also be odd, or must end in a particular digit.

## Wrapping Up

The power of this activity lies in its blend of learning and fun. It promotes engagement, facilitates mathematical discourse, and encourages students to explore and experiment with numbers. By the end of it, students will have the rule of divisibility by 7 ingrained in their minds!

This game aligns with the Common Core State Standards (CCSS), particularly CCSS.MATH.CONTENT.4.OA.B.4 – Recognize that a whole number is a multiple of each of its factors. Determine whether a given whole number in the range 1-100 is a multiple of a given one-digit number.

While the rule for divisibility by 7 may not work every time, it offers a valuable opportunity for students to engage with numbers and reasoning in a way that goes beyond rote learning. So, why wait? Set the stage for this fun-filled mathematical adventure and let the magic of learning take over!