NIELIT 2016 MAR Scientist B - Section A: 11

Question

Have a look at the series : $2,1,(1/2),(1/4),\dots$ What number should come next?

• A. $(1/3)$
• B. $(1/8)$
• C. $(2/8)$
• D. $(1/16)$

Answer 1

Method1: It is a series of numbers where the next number is half of its previous number.

2/2 = 1
1/2 = 1/2
(1/2)/2 = 1/4
(1/4)/2 = 1/8 

option B is correct. 

Method 2:The above sequence is a GP (geometric progression) with the first term 2, and the common ratio 1/2.

$ n^th$ term of GP = $ a r^(n−1)$

 

So, fifth term of GP = $2*(1/2)^4$

                                =$2 * (1/16)$

                                = $1/8$

So, next term of GP = $1/8$