Is the following sequence geometric? If so, what is the common ratio?

1, 3, 6, 18, 36, ...

No

Step-by-step explanation:

For the sequence to be geometric a common ratio r must exist between consecutive terms.

3 : 1 = 3

6 : 3 = 2

18 : 6 = 3

36 : 18 = 2

The ratio between consecutive terms is not equal thus not geometric.

Yes

Step-by-step explanation:

Multiply 1 by 3 (1.3=3) Then the result you multiply by 2 (you alternate multiplying by 3 then by 2 then by 3 ...

1 * 3 = 3

3 * 2 = 6

6 * 3 = 18

18 * 2 = 36