Session 31: The Least Common Multiple (LCM)

Session Title	The Multiple Mysteries
Objective	By the end of this session, students will be able to: 1. Understand the concept of the Least Common Multiple (LCM) 2. Find the LCM of the given numbers using different methods. 3. Develop problem-solving and teamwork skills
Topics	The Least Common Multiple (LCM) is the smallest multiple that two or more numbers share. It is useful in real-life applications, such as scheduling events, solving fraction problems, and understanding patterns.
Material Required	Board & Chalk Before starting the class, draw a number grid ( up to 50 ) on the floor
Methodology	Activity-based Learning: Physical activity and group work. Experiential Learning: Relating LCM to real-life situations.
Session Duration	90 Minutes

Introduction Activity(10 Minutes)

Pass pass

In "Pass Pass," children form a circle. Choose any number, for example 5. Then each child starts counting from one. When they reach 5 or multiples of five, they have to say pass. If they don't say pass, that child is out. The game continues until only one child remains.(NB: Change the number after each round)

Main Activity(70 minutes)

Tell a short story:- ( 20 minutes )

Two friends, Arya and Rahul, love visiting a park. Arya visits every 3 days, and Rahul visits every 4 days. If both visit the park today, when will they meet again?

Ask students to think and predict: “Will they meet again in a week? In 10 days?”

Guide them to count the days until both are at the park together (on the 12th day).

Explain that the Least Common Multiple (LCM) of 3 and 4 is 12—the smallest number that both 3 and 4 can divide into evenly.

Game Time ( 25 minutes )

Draw a number grid on the floor (1–50)
Call out two numbers (e.g., 4 and 6)
Students take turns hopping on the multiples (4, 8, 12… and 6, 12, 18…)
The first common number they step on is the LCM ( NB: Repeat the activity with different number )

Time to solve ( 20 Minutes)

Give simple examples: ( Divide students into small groups)

LCM of 2 and 5

→ Multiples: (2, 4, 6, 8, 10, 12…) and (5, 10, 15…) → LCM is 10.

LCM of 6 and 8

→ Multiples: (6, 12, 18, 24…) and (8, 16, 24…) → LCM is 24.

A bell rings every 6 minutes, and another bell rings every 8 minutes. After how many minutes will both bells ring together?
A school organizes a sports day every 5 years, and a cultural fest every 7 years. How many years later will both events happen together again?

Review Questions(5 minutes)

Ask: What strategies helped you solve the problems quickly?

Encourage peer teaching—students explain their solutions to classmates.

Follow up Task (10minutes)

Home work

1.Two farmers plant crops—one plants every 9 days, and the other every 12 days. In how many days will they plant on the same day again?

2.Two buses leave a station at the same time—one after 12 minutes, the other after 15 minutes. When will they leave together again?

Expected Learning Outcome:

Knowledge building-

Concept of LCM
Method to find LCM

Skill Building-

Logical thinking
Strengthens speed and accuracy
Team work