5.3"
15, 30, 45, 60
5, 15, 45, 135
0, 15, 45, 135
15, 45, 135, 405
The common ratio between each term is 3. Therefore, the next number in the sequence would be:
180, 540, 1620, 4860
15, 30, 45, 60
5, 15, 45, 135
0, 15, 45, 135
15, 45, 135, 405
180, 540, 1620, 4860