# #20, 10, 2.5# ?

##### 1 Answer

See explanation...

#### Explanation:

It is not clear what this question is asking.

Some possibilities:

**What is the next number in the sequence #20, 10, 2.5# ?**

Note that

#2.5 / 6 = 0.41bar(6)#

or

#2.5 / 8 = 0.3125#

Since this does not fall into the category of any standard sequence, we could justify all kinds of continuations of the sequence.

**What number is missing in the geometric sequence #20, 10, 2.5#?**

Note that the sequence:

#20, 10, color(red)(5), 2.5#

would be a geometric sequence, with each term being half of the preceding one.

**What is the rule and next term of the sequence #20, 10, 5, 2.5#?**

Note this assumes that

If so, then this looks like a geometric sequence with initial term

The formula for a general term would be:

#a_n = 20*(1/2)^(n-1)#

and the next term of the sequence would be:

#2.5*(1/2) = 1.25#