Let us take an example shown in the video.

We want to find HCF of 455 and 42

Now, divide 455 by 42, we get

10 as quotient and 35 as remainder.

Again, we divide 42 by 35, we get

1 as quotient and 7 as remainder.

Again we divide 35 by 7 we get

5 as quotient and 0 as remainder.

When we get remainder 0 and the number from which we divide last time, is the HCF

So, HCF(455, 42) = 7

In this way, we find the HCF.

Hope you got the point.