Find missing number in the series 9 ,19 ,40 ,? ,170

Question

Find the missing number.
13, 11, 31
19, 9, 17
23, ?, 25

Answer 1

Ans : 83

Here is the solution:

i =  1;     (increment it by one for next number)
next_number = (number * 2) + i

(9  * 2) + 1 = 19
(19 * 2) + 2 = 40
(40 * 2) + 3 = 83   ===> (this is the ans)
(83 * 2) + 4 = 170

Answer 2

Missing number is 83. Double the number and go on adding 1,2,3 ,4... to get the next number.