SOLUTION: complete the pattern 9, 1, 11, 5, 13, 19, ... what would be the last number and why?

1st term = 9
2nd term = 1
3rd term = 11
4th term = 5
5th term = 13
6th term = 19


Look at the odd-numbered term:

1st term = 9
3rd term = 11
5th term = 13
...

That obvious goes 9,11,13,15,17,19,..., the odd numbers starting with 9.

Now look at the even numbered terms:

2nd term = 1
4th term = 5
6th term = 19

  1+ 4=5
  5+14=19
 19+24=43
 43+54=97 
 97+64=161
161+74=235
...

That obviously goes this way: start with 1, add 4, then add 10 more than 4, or 14. 
the add 10 more than you added last time.

So the sequence goes like this:

9, 1, 11, 5, 13, 19, 15, 43, 17, 97, 19, 161, 21, 235, ...

Edwin