Find the invalid no.from the following series 15 46 63 71 75 77 78  Choices
A) 38
B) 43
C) 46
D) 49
E) 52
In this question, if you start from the beginning, firstly the difference is 31, then the difference is 17, then the difference is 8. So there is no logic. If you start backwards,you can see that firstly, 1 is added, then 2 is added, then 4 is added, then 8,16 and 32 should have been added. So you have got the right clue. So 15 + 32 the first number should be 47 and afterwards, the series becomes + 16, + 8, + 4and so on.   46
<result>C</result>
Find the invalid no.from the following series 15 46 63 71 75 77 78