Which of the following is a common multiple of 2, 3 and 9?

The correct option is B 36



As we can see, 24 and 30 are common multiple of 2 and 3, but not 9.
33 is neither a multiple of 2 or 9, only 3.

Only the numbers that occur in the common part of all three circles are the common multiples of 2, 3, and 9.

Hence, out of all the options, only 36 is the common multiple of 2, 3 and 9.

There can be an infinite number of common multiples of these three numbers, we have just made the diagram for numbers close to the numbers in options.