Aptitude - Odd Man Out and Series - Discussion

Insert the missing number.

1. 

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

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

Answer: Option A

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.

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