The two common multiples of three and five are: 15 and 30 ^-^
15 and 30
Multiples of 15 include 15, 30 and 45. For them to be common, they need to be compared to another set of multiples.
There are infinite common multiples for a set of numbers. So it is not possible to write down all the common multiples. Some common multiples of 15, 30 and 45 are 90, 180, 270, 360,... There is another way to find common multiples: Write the multiples of LCM(15, 30, 45). Actually the common multiples of a set of numbers are the multiples of their LCM. LCM of 15, 30 and 45 is 90. And the multiples of 90 are 90, 180, 270, 360, 450, 540,... which are the common multiples of 15, 30 and 45.
30 is a multiple of 30 and 15.
They are any multiples of 30
The multiples of 15 are 15, 30, 45, 60, 75 and so on. For them to be common, they need to be compared to another set of multiples.
30 and all its multiples
Multiples of 15 include 15, 30 and 45. For them to be common, they need to be compared to another set of multiples.
The multiples of 3 up to 30 are: 3,6,9,12,15,18,21,24,27,30.The multiples of 5 up to 30 are: 5,10,15,20,25,30.The only common multiples are 15 and 30.The LCM is: 30
The multiples of 20 are 20, 40, 60, 80, 100, 120... The multiples of 30 are 30, 60, 90, 120, 150... The multiples of 15 are 15, 30, 45, 60, 75, 90, 105, 120, 135... The common multiples of 20, 30, and 15 are 60, 120, 180, 240...
Do you mean common multiples? If so, then 30, 60, 90 etc. are common multiples of 30 and 5. If you mean multiples of 5 and factors of 30, that's 5, 15 and 30.