28 and 56
20 and 40.
You have to have two different numbers to find common multiples
The two common multiples of three and five are: 15 and 30 ^-^
Two common multiples of 21 and 15 are 105 and 315.
Those are known as "common multiples". The smallest POSITIVE of these common multiples is called the "least common multiple".
They are the common multiples of the two numbers.
60 and 120 are the two lowest common multiples.
The common multiples of 9 and 16 are 144, 288, 432 and so on.
common multiples
The two smallest multiples of 10 are 10 and 20. For them to be common, they would need to be compared to another set of multiples.
All multiples of 36 are multiples of 18.
All multiples of 64 are multiples of 8.