Find the least common multiple (LCM) of $18$ and $24$ .

medium 2 marks Class 6 · Mathematics · Knowing Our Numbers

Answer

72

The correct answer is $72$ — Therefore the LCM of $18$ and $24$ is $72$ .

Step-by-step solution

Prime‑factorise $18$ : $18 = 2 \times 3 \times 3 = 2 \times 3^{2}$ .
Prime‑factorise $24$ : $24 = 2 \times 2 \times 2 \times 3 = 2^{3} \times 3$ .
Take the highest power of each prime that appears: for $2$ it is $2^{3}$ , for $3$ it is $3^{2}$ .
Multiply these: $2^{3} \times 3^{2} = 8 \times 9 = 72$ .
Therefore the LCM of $18$ and $24$ is $72$ .

Common mistake: Multiplying the numbers together instead of finding the LCM

Concept tested: LCM using prime factorisation