Number Series Puzzles - 7

1.  Which number should replace the question mark ?

     6,13,27,55,?

A:-  111

        6
        6*2 = 12+1 = 13
        13*2 = 26+1 = 27
        27*2 = 54+1 = 55
        55*2 = 110+1 = 111.

2.  Look at this series : 22,21,23,22,24,23,...... What number should come next ?

A:-  25

       22
       22-1 = 21
       21+2 = 23
       23-1 = 22
       22+2 = 24
       24-1 = 23
       23+2 = 25.

3.  What number should replace the question mark ?

     21,32,45,60,?,96,117,140.

A:-  77

       21
       21+11 = 32
       32+13 = 45
       45+15 = 60
       60+17 = 77
       77+19 = 96
       96+21 = 117
      117+23 = 140.

4.  Look at this series : 53,53,40,40,27,27,.... What number should come next ?

A:-  14

        53
        53
        53-13 = 40
                      40
        40-13 = 27
                      27
        27-13 = 14
                      14.