Which number can be used as a counter example to, "Any number that is divisible by 3 is divisible by 9"?

Question

a)9, b)18, c)30, d)40
Can you explain me the answer how do you get it? because I don't understand about counter examples. Thanks

Answer 1

Study this site for an explanation of counter example.

http://www.icoachmath.com/math_dictionary/Counter_Example.html

Now, looking at your answer choices.

9 is divisible by both 3 and 9
18 is divisible by both 3 and 9
30 is divisible by 3 -- but NOT by 9