Aptitude - Odd Man Out and Series - Discussion
Discussion Forum : Odd Man Out and Series - Find Wrong No. (Q.No. 10)
Directions to Solve
Find out the wrong number in the series.
10.
3, 7, 15, 39, 63, 127, 255, 511
Answer: Option
Explanation:
Go on multiplying 2 and adding 1 to get the next number.
So, 39 is wrong.
Discussion:
8 comments Page 1 of 1.
Nani said:
7 years ago
All are divisible by 3. But 7 can't be divisible. So, why can't that be the answer?
(2)
R@m said:
8 years ago
The another logic is 2^2 - 1, 2^3 - 1, 2^4 - 1, .....
(1)
Poooja said:
8 years ago
Thank you for your clear answer.
Mehtab said:
9 years ago
3*2 + 1 = 7
7*2 + 1 = 15
15*2 + 1 = 31
31*2 + 1 = 63
63*2 + 1 = 127
127*2 + 1 = 255
255*2 + 1 = 511
31 is given instead of 31.
39 is the wrong answer.
7*2 + 1 = 15
15*2 + 1 = 31
31*2 + 1 = 63
63*2 + 1 = 127
127*2 + 1 = 255
255*2 + 1 = 511
31 is given instead of 31.
39 is the wrong answer.
(1)
Siva said:
9 years ago
Please clear explain.
(1)
Grace said:
1 decade ago
3+4 = 7.
7+8 = 15.
15+16 = 31.
31+32 = 63.
63+64 = 127.
127+128 = 255.
255+256 = 511.
.
.
7+8 = 15.
15+16 = 31.
31+32 = 63.
63+64 = 127.
127+128 = 255.
255+256 = 511.
.
.
(2)
Shruti said:
1 decade ago
It can also be solved like such---
2^2-1,2^3-1,2^4-1,2^5-1 and so on....
2^2-1,2^3-1,2^4-1,2^5-1 and so on....
(1)
Ashik Mohammed Nazar said:
1 decade ago
3,7,15,39,63,127,255,511
If u closely look at this pattern,and the differences between the consecutive numbers,
It is 4 8 24 24 64 128 256
By changing 39 to 31, the differences become
4 8 16 32 64 128 256 which is
2^2 2^3 2^3 2^4 and so on ...
If u closely look at this pattern,and the differences between the consecutive numbers,
It is 4 8 24 24 64 128 256
By changing 39 to 31, the differences become
4 8 16 32 64 128 256 which is
2^2 2^3 2^3 2^4 and so on ...
(2)
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