Question

Write the first five multiples of $10$ and $20$. Highlight their common multiple and find their LCM.

Answer 1

Multiples of $10$:

$10,\text{20},30,\text{40},50$

Multiples of $20$

$\text{20},\text{40},60,80,100$

Common multiples of $10$ and $20$ are $20,40$

To find $\text{LCM}$ of $20$ and $40$, we need to write these numbers in the form of product of their prime factors:

$20=2\times 2\times 5=2^2\times 5$

$40=2\times 2\times 2\times 5=2^3\times 5$

$\text{LCM(20,40)}=2\times 2\times 2\times 5$

$=40$ Ans