Consider the numbers $100$100 and $42$42.
List all the factors of $100$100. Write them all on the one line separated by a comma.
List all the factors of $42$42. Write them all on the one line separated by a comma.
Hence find the highest common factor of $100$100 and $42$42.
Consider the numbers $36$36 and $4$4.
What is the highest common factor of $8$8 and $6$6?
What is the highest common factor of $40$40 and $70$70?