Last updated on May 26th, 2025
The smallest positive integer that divides the numbers with no numbers left behind is the LCM of 2,4 and 5. Did you know? We apply LCM unknowingly in everyday situations like setting alarms and to synchronize traffic lights and when making music. In this article, let’s now learn to find LCMs of 2,4 and 5.
We can find the LCM using listing multiples method, prime factorization method and the long division method. These methods are explained here, apply a method that fits your understanding well.
Step 1: List the multiples of each of the numbers;
2 = 2,4,6,8,10,12,14,16,18,20,…
4= 4,8,12,16,20,…
5= 5,10,15,20,…
Step 2: Find the smallest number in both the lists
LCM (2,4,5) = 20
2 = 2
4 = 2×2
5 = 5
LCM(2,4,5) = 20
Listed here are a few mistakes children may make when trying to find the LCM due to confusion or due to unclear understanding. Be mindful, understand, learn and avoid!
A number is divisible by 4 and 5, and also by 2. Find the missing number if the LCM of 2, 4, and the missing number is 20.
Since LCM(2, 4, x) = 20,
we know x must be a divisor of 20. The prime factorization of 20 is 22×5, so x must include a factor of 5. Thus, the missing number is 5.
The LCM of any number that already includes the factors of 2 and 4 would need an additional factor of 5 to make 20, leading to x = 5.
Find the smallest number divisible by 2, 4, and 5 that leaves a remainder of 1 when divided by 3.
The LCM of 2, 4, and 5 is 20.
Now, find the smallest multiple of 20 that leaves a remainder of 1 when divided by 3.
20÷3=6 remainder 2,
so the next multiple to check is 20 + 1 = 21.
Therefore, the smallest number divisible by 2, 4, and 5 that leaves a remainder of 1 when divided by 3 is 21.
The LCM ensures divisibility by 2, 4, and 5. We then search for the smallest number of the form 20k + 1 that satisfies the remainder condition.
Compare the LCM of 2, 4, and 5 with the LCM of 3, 6, and 9. Which is larger?
LCM(2, 4, 5) = 20
LCM(3, 6, 9):
Prime factorization;
3 = 3
6 = 2 × 3
9 = 3²
LCM(3, 6, 9) = 2 × 3² = 18
Therefore, LCM(2, 4, 5) = 20 is larger than LCM(3, 6, 9) = 18.
This problem demonstrates how the LCM can be used to compare sets of numbers with different prime factorizations.
Hiralee Lalitkumar Makwana has almost two years of teaching experience. She is a number ninja as she loves numbers. Her interest in numbers can be seen in the way she cracks math puzzles and hidden patterns.
: She loves to read number jokes and games.