the common multiples between 1 and 100 for 9 and 10 are just 90!
I presume you mean what are all the multiples of 9 up to 100 (and not what are all the multiples of 9, 10, 11, ..., 100 of which there are infinitely many): 9, 18, 27, 36, 45, 54, 63, 72, 81, 90, 99.
9,18,27,36,45,54,63,72,81,90,99
Multiples of 9 up to 100 are 9, 18, 27, 36, 45, 54, 63, 72, 81, 90, 99. Multiples of 10 up to 100 are 10, 20, 30, 40, 50, 60, 70, 80. 90, 100. The only common multiple up to 100 of 9 and 10 is 90.
There are 11 multiples of 9 up to 100. 9 18 27 36 45 54 63 72 81 90 99
100 of them.
11
9,18,27,36,45,54,63,72,81,90,99
Just 72. It was found by multiplying 8 and 9. --------------------------------------- The common multiples of two numbers are the multiples of their lowest common multiple. LCM(8, 9) = 72 The common multiples of 8 and 9 are 72, 144, 216, ... The only common multiples less than 100 are 72 only.
11
110.
9,18,27,36,45,54,63,72,81,90,99