# Aptitude - Odd Man Out and Series - Discussion

Discussion Forum : Odd Man Out and Series - Find Wrong No. (Q.No. 9)
Directions to Solve
Find out the wrong number in the series.

9.
40960, 10240, 2560, 640, 200, 40, 10
640
40
200
2560
10240
Explanation:

Go on dividing by 4 to get the next number.

So, 200 is wrong.

Discussion:
8 comments Page 1 of 1.

Ravi said:   4 years ago
40960 = 64^2 * 10.
10240 = 32^2 * 10.

And so on but 200 can't be written like this.

Niharika said:   7 years ago
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.

Gowri rudra said:   8 years ago
According to other procedure 640 is also one of the answer.

Satya said:   9 years ago
How to understand that we have to divide by 4?

Priyanka said:   9 years ago
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 :).
(2)

Akshay said:   10 years ago
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.

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.