LCM of 20 and 40 is 40. The full form of LCM is least common multiple. Students get confused about choosing the right material among various for effective learning. For this purpose, subject matter experts designed the article Prime Factorisation and Division Method for LCM and HCF to help students grasp the concept of LCM and HCF more effectively. Referring to this article while solving problems also enhances the skills required to score good marks in academics. Let us learn how to find the least common multiple of 20 and 40 with solved examples and FAQs in detail here.
What is LCM of 20 and 40?
The Least Common Multiple of 20 and 40 is 40.
How to Find LCM of 20 and 40?
LCM of 20 and 40 can be determined by using the method given below:
- Prime Factorisation
- Division method
- Listing the multiples
LCM of 20 and 40 Using Prime Factorisation Method
By prime factorisation method, we can write 20 and 40 as the product of prime numbers, such that;
20 = 2 × 2 × 5
40 = 2 × 2 × 2 × 5
LCM (20, 40) = 2 × 2 × 2 × 5 = 40
LCM of 20 and 40 Using Division Method
In division method, to calculate the LCM, we divide the numbers 20 and 40 by their prime factors until we get the result as one in the complete row. The product of these divisors represents the least common multiple of 20 and 40.
| 2 | 20 | 40 |
| 2 | 10 | 20 |
| 2 | 5 | 10 |
| 5 | 5 | 5 |
| x | 1 | 1 |
No more further division can be done.
Hence, LCM (20, 40) = 2 × 2 × 2 × 5 = 40
LCM of 20 and 40 Using Listing the Multiples
To calculate the least common multiple of 20 and 40 using listing multiples, we list out the multiples of 20 and 40. The multiples of 20 and 40 are shown in the below table.
| Multiples of 20 | Multiples of 40 |
| 20 | 40 |
| 40 | 80 |
| 60 | 120 |
| 80 | 160 |
| 100 | 200 |
| 120 | 240 |
| 140 | 280 |
LCM (20, 40) = 40
Related Articles
Video Lesson on Applications of LCM
Solved Examples
Q. 1: The GCD and LCM of the two numbers are 20 and 40. If one number is 40, calculate the other number.
Solution: Let the other number be m
We know that,
GCD × LCM = 40 × m
m = (GCD × LCM) / 40
m = (20 × 40) / 40
m = 20
Hence the other number is 20.
Q. 2: Find the LCM of 20 and 40 by division method.
Solution: We can find the LCM of 20 and 40 by division method as below
| 2 | 20 | 40 |
| 2 | 10 | 20 |
| 2 | 5 | 10 |
| 5 | 5 | 5 |
| x | 1 | 1 |
LCM (20, 40) = 2 × 2 × 2 × 5 = 40
Therefore the least common multiple of 20 and 40 by division method is 40.
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