Number Series Puzzles - 8

1.  What number should replace the question mark ?
 
      1,2,5,10,17,26,37,?

A:-  50

       1
       1+1 = 2
       2+3 = 5
       5+5 = 10
       10+7 = 17
       17+9 = 26
       26+11 = 37.

2.  Look at this series: 31,29,24,22,17,...... What number should come next ?

A:-  15

        31
        31-2 = 29
        29-5 = 24
        24-2 = 22
        22-5 = 17
        17-2 = 15.

3.  What number should replace the question mark ?

      13,17,21,25,?

A:-  29

       13
       13+4 = 17
       17+4 = 21
       21+4 = 25
       25+4 = 29.

4.  Look at this series: 3,4,7,8,11,12,..... What number should come next ?

A:-  15

       3
       3+1 = 4
       4+3 =7
       7+1 = 8
       8+3 = 11
       11+1 = 12
       12+3 = 15.