geomatric series

In simple words, a normal geometric series with first term $a=2$ and common ratio $r= \frac{1}{2}$ .

We have $4$ terms there, so we need to find out the $5th$ term.

Therefore, $a_{5} = ar^{5-1} = 2\times0.5^{4} = 2 \times \frac{1}{16} = \boxed{\frac{1}{8}}$

This is a simple division series; each number is one-half of the previous number.

In other terms to say, the number is divided by 2 successively to get the next result.

4/2 = 2 2/2 = 1 1/2 = 1/2 (1/2)/2 = 1/4 (1/4)/2 = 1/8 and so on.