What is the next number in this series? 2 1 .5 .25 .125

Answer 1

Just look at the ratios:

1/2 = 0.5
.5/1 = 0.5
.25/.5 = 0.5
...

So, the next number is .125 * .5 = .0625

It might have been easier using fractions. The sequence is thus seen to be

2, 1, 1/2, 1/4, 1/8, ...

Answer 2

thank you