# Aptitude - Odd Man Out and Series - Discussion

### Discussion :: Odd Man Out and Series - Missing No. (Q.No.1)

Insert the missing number.

1.

16, 33, 65, 131, 261, (....)

 [A]. 523 [B]. 521 [C]. 613 [D]. 721

Explanation:

Each number is twice the preceding one with 1 added or subtracted alternatively.

So, the next number is (2 x 261 + 1) = 523.

 Fcd said: (Oct 21, 2011) So that way I calculate the number 131*2+1=263 here I got 263 what's the correct answer?

 Sou said: (Nov 12, 2011) Adding and subtracting 1 alternatively so (2*16+1)=33 (2*33-1)=65 (2*65+1)=131 (2*131-1)=261 (2*261+1)=523 Therefore 523 is correct.

 Pooja said: (Nov 12, 2011) Here 16*2+1=33 2*33-1+65 2*65+1=131 2*131-1=261 2*261+1=523

 Dolly said: (May 30, 2015) Then the answer could b even 521 as 2*261-1 = 521, when we can sub 1 from the above one that is 2*131-1. Why not from 261?

 Bipin Parida said: (Mar 7, 2016) 16*2+1 = 33. 2*33-1 = 65. 2*65+1 = 131. 2*131-1 = 261. 2*261+1 = 523.

 123 said: (Oct 8, 2016) Yes, 523 is the correct answer.

 Kartik Sharma said: (Mar 20, 2017) See, if we square the number and then divide by half of it and add 1 and subtract 1 in alternative way wise we will get the number. Method :- 16 * 16 = 256 , 256 / 8 = 32 , 32+1 = 33. 33 * 33 = 1089 , 1089 / 16.5 = 66 , 66 -1 = 65. 261 * 261 = 68121 , 68121 / 130.5 = 522 , 522 + 1 = 523.

 B.T.L.Aruna said: (Jul 13, 2019) 16*2+1 = 33. 2*33-1 = 65. 2*65+1 = 131. 2*131-1 = 261. 2*261+1 = 523.

 Danny said: (Aug 27, 2019) If each number is twice the preceding number with 1 added or subtracted then why isn't the answer 521?

 Neeraj Kumar said: (Sep 24, 2019) 16 * 2 + 1 = 33. 33 * 2 - 1 = 65. 65 * 2 + 1 = 131. 131 * 2 - 1 = 261. 261 * 2 + 1 = 523.

 Karthik said: (May 28, 2020) 16+16=32+1 = 33, 33+33=66-1 = 65, 65+65=130+1 = 131, 131+131=262-1 = 261, 261+261=522+1 = 523.

 Supriya said: (Apr 1, 2021) 16+16 = 32 + 1 = 33. 33+33 = 66 - 1 = 65. 65+65 = 130 + 1 = 131. 131+131 = 262 - 1 = 261. 261+261 = 522 + 1 = 523. Hence 523 is the answer.