What is the multiples of 15?

Answer 1

Nothing: it is not defined.

Multiplication is a binary operation and that means it is defined for two numbers. You can multiply one number by another number (which could have the same value), but there is no meaning to multiplication of just one number.

Answer 2

15, 30, 45, 60, 75, 90, 105, 120, 135, 150, . . .

Answer 3

To find a multiple, multiply your number by successive counting numbers.

1.5 x 1 = 1.5

1.5 x 2 = 3

1.5 x 3 = 4.5

and so on.