Ib maths puzzles

There are a lot of good general sequence puzzles on the website Fibonicci.

For example find the next term of:

1) 15, 29, 56, 108, 208

2) 13, -21, 34, -55, 89

3) 52, 56, 48, 64, 32

4) 230, 460, 46, 92, 9.2

5) 68, 36, 20, 12, 8

Answers (in white text – highlight to reveal)

1) 400
2) -144
3) 96
4) 18.4
5) 6