Question

What should the next number be? 100 96 104 88 120 56

Answer 1

100 ---> 96 is -4

96 ---> 104 is +8

104 ---> 88 is -16

88 ---> 120 is +32

120 ---> 56 is -64  

So first we go down by 4, then up by 8, then down 16, then up 32, then finally down 64.  

The pattern of numbers is: -4, +8, -16, +32, -64  

Notice it's the powers of 2:  

2^2 = 4

2^3 = 8

2^4 = 16

2^5 = 32

2^6 = 64

each term doubles. Also each term alternates in sign. One is positive, then the next is negative and so on.  

The last difference is -64, which doubles to -128. Change the sign to positive to get +128  

Add 128 to the last term of 56 to get

128+56 = 184  

Therefore, the final answer is 184