Question

Find the missing number in the circle:

A. \[66\]
B. \[72\]
C. \[71\]
D. \[78\]

Answer 1

Hint: To find the missing value we first need to find the pattern in which the numbers are going in the circle. To find the pattern we need a much arithmetic process like multiplication, division, subtraction etc. Here in this case we can see that the numbers are doubled and then subtracted by consecutive natural numbers.

Complete step-by-step answer:
The numbers used in this pattern are given as: \[5,8,13,22,39,?\]
The numbers are in difference of power of two as:
The difference between the first two number is:
 \[5\times 2-2=8\]
The difference between the second and third number is:
 \[8\times 2-3=13\]
The difference between the third and the fourth number is:
 \[13\times 2-4=22\]
The difference between the fourth and the fifth number is:
 \[22\times 2-5=39\]
The difference between the fifth and the sixth number is:
 \[39\times 2-6=?\]
Therefore, the value of the question mark is given as \[72\] .
So, the correct answer is “72”.

Note: The series can also be written backward that is from \[?,39,22,13,8,5\] . Hence, the series’s first term can be found by using the formula as:
 \[\dfrac{?+6}{2}=39\] .