Number Series Puzzles - 2

1.  Which number is missing ?

      1,8,27,64,?

A:-  125

        1*1*1 = 1
        2*2*2 = 8
        3*3*3 = 27
        4*4*4 = 64
        5*5*5 = 125.

2.  Which number completes this sequence ?

      123,117,108,99,?

A:-  81

        123
        1+2+3 = 6    123-6 = 117
        1+1+7 = 9    117-9 = 108
        1+0+8 = 9    108-9 = 99
        9+9 = 18      99-18 = 81.

3.  What comes next in this series ?

      1,2,6,24,120,720,?

A:-  5040

       1
       1*2 = 2
       2*3 = 6
       6*4 = 24
       24*5 = 120
      120*6 = 720
      720*7 = 5040.