Aptitude - Odd Man Out and Series - Discussion

Find out the wrong number in the series.

9. 

40960, 10240, 2560, 640, 200, 40, 10

[A]. 640
[B]. 40
[C]. 200
[D]. 2560
[E]. 10240

Answer: Option C

Explanation:

Go on dividing by 4 to get the next number.

So, 200 is wrong.


Madhu said: (Sep 23, 2011)  
The answer should be 640. Because when it divided by 4, it does net get the next number.

Indhumathi said: (Jan 22, 2013)  
No, answer is 200 because

40960/4 is 10240.
10240/4 is 2560.
2560/4 is 640.
640/4 is 160.

But here they give 200, see
160/4=40 next number will be correct,

So the answer is 200, here 200 is wrong.

Akshay said: (Feb 23, 2014)  
It has perfect square and it multiply by 10. But in 10, 200, 10240.

It is not an perfect square. In option 10 and 10240 is not given so it has out of choice. Hence 200 is correct.

Priyanka said: (Sep 2, 2014)  
10 40 200 640 2560 10240 40960

Multiply by 4,

10*4 = 40.
40*4 = 160.
160*4 = 640.
640*4 = 2560..... Instead of 160 there is 200. So answer is 200.

Blind method
----------------
Observer last two digits.. in series.
40960, 10240, 2560, 640, 200, 40, 10

60, 40, 60, 40, 00, 40, 10

So 10 is not in Answer option.
So 00 is the answer == 200 :).

Satya said: (Oct 31, 2014)  
How to understand that we have to divide by 4?

Gowri Rudra said: (Feb 5, 2016)  
According to other procedure 640 is also one of the answer.

Niharika said: (May 17, 2017)  
From the last term of the series: (consider " * " as "to the power of").

10 x 2 * 0 = 10
10 x 2 * 2 = 40
10 x 2 * 4 = 160(not 200 which is given)
10 x 2 * 6 = 640
10 x 2 * 8 = 2560
10 x 2 * 10 = 10240
10 x 2 * 12 = 40960.

Ravi said: (Jun 10, 2019)  
40960 = 64^2 * 10.
10240 = 32^2 * 10.

And so on but 200 can't be written like this.
So 200 is the answer.

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