   What is the next number in the following series - 9 , 19 , 39 , 79 , ??

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What is the next number in the following series - 9 , 19 , 39 , 79 , ?? posted Sep 1, 2014

As per the given series ( 9, 19, 39, 79 .. ?)

next_number = (number + 10 * (1, 2, 4, 8, ..)), i.e

9  + (10 * 1) = 19
19 + (10 * 2) = 39
39 + (10 * 4) = 79
79 + (10 * 8) = 159

One more solution is:
next_number = (number * 2) + 1

9 * 2 + 1  = 18  + 1 ==> 19
19 * 2 + 1 = 38  + 1 ==> 39
39 * 2 + 1 = 78  + 1 ==> 79
79 * 2 + 1 = 158 + 1 ==> 159 answer Sep 1, 2014 answer Sep 1, 2014 by anonymous

159
9x2+1=19,19x2+1=39,39x2+1-79,79x2+1=159 answer Oct 26, 2014

(9*2) + 1 = 19
(19*2) + 1 = 39
(39*2) + 1 = 79
(79*2) + 1 = 159

So answer is 159 answer Nov 4, 2014

10 added to 9, to get 19.
Double of 10, 20 added to 19 to get 39.
Double of 20, 40 added to 39 to get 79.
Double of 40, 80 added to 79 to get 159. answer Sep 2, 2016

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