Question

Write the next number of each of the following figure:
4,9,19,39,___

Answer 1

★ $\texttt{\large{Answer :}}$

$\textsf{\large{79}}$

★ $\textsf{\large{Explaination}}$

★ $\textsf{The Logic of the series :}$

• The difference between the first numbers = 9 - 4

= 5

• The difference between the next numbers = 19 - 10

= 10

• The difference between the next numbers = 39 - 19

= 20

• So, from the above explaination we can deduce that one number is added by x number, so in the next 2 numbers it becomes 2x.

• As observed above, the difference between 9 and 4 is 5.

• Whereas the next two numbers 19 and 9 has difference is 10 ( 5+5 ) or (5 × 2)

• It continues ahead with 39 and 19. 39-19 gives 20 (10+10) or (10×2)

• So, according to the logic above the next term :

$\textsf{=> 39 + (20+20)}$

$\textsf{=> 39 + 40}$

$\textsf{=> 79}$

$\therefore$$\textsf{\large{The next term is 79}}$