Aptitude - Odd Man Out and Series - Discussion

Find the odd man out.

2. 

8, 27, 64, 100, 125, 216, 343

[A]. 27
[B]. 100
[C]. 125
[D]. 343

Answer: Option B

Explanation:

The pattern is 23, 33, 43, 53, 63, 73. But, 100 is not a perfect cube.

Gayathri Ram said: (Jun 29, 2011)  
We can do this problem by another method also. See the sequence. If you remove 100 then you can see continuous even odd sequence.

8=even.

27=odd.

64=even.

125=odd.

216=even.

343=odd.

If you see that there will continuous even, odd sequence. Since 100 comes next to 64. Definitely it is an wrong no.

Nazneen said: (Jul 13, 2011)  
Thanks gayitri ram, you made we. Easy.

Meena said: (Nov 28, 2011)  
Thanks a lot gayathri ram.

B D Vekaria said: (Dec 17, 2011)  
Thanks You made easy.

Let me ask questions to find wrong number

a) 1 3 6 11 20 39 70

b) 50 51 47 56 42 65 29


Formulae for sum of even numbers from 0 - 40 ?

Jincy said: (Feb 16, 2012)  
Answer to the first series is 39.
Let the numbers be t(0), t(1), etc
To get the nth term : t(n) = t(n-1) + 1 + 2^(n-1)

3 = 1 + 1 + 2^0
11 = 6 + 1 + 2^2
20 = 11 + 1 + 2^3
next number will be 20 + 1 + 2^4 = 37

Prashant Kumar Singh said: (Feb 21, 2012)  
@Gayathri

You are right but this question also we can solve by another method like-
8=8
27=2+7=9
64=6+4=10

100=1+0+0=1

125=1+2+5=8
216=2+1+6=9
343=3+4+3=10

So wrong answer is 100.

Sonutalwani said: (Jun 27, 2012)  
2*2*2=8.

3*3*3=27.

4*4*4=64.

5*5*5=125.

6*6*6=216.

7*7*7=343.

But 100 is not a perfect cube.

Rathiga said: (Jan 2, 2013)  
2^3=8
3^3=27
4^3=64
5^3=125
6^3=216
7^3=343

So wrong answer is 100.

Shameem Khan said: (Aug 24, 2013)  
8=8.
27=2+7=9.
64=6+4=10.
100=1+0+0=1.
125=1+2+5=8.
216=2+1+6=9.
343=3+4+3=10.

Answer = 100. Except 100 remaining all are in series.

Alok said: (Dec 16, 2014)  
All are cube except 100. So answer is 100.

Manickavel M said: (Feb 18, 2015)  
Very good mental ability.

Poornima said: (Apr 18, 2015)  
For the first one - I can even conclude that 343 is the answer because it is the only prime number. Why is that also not a valid answer?

Sudheer Reddy said: (Aug 14, 2015)  
2^3=8.
3^3=27.
4^3=64.
5^3=125.
6^3=216.
7^3=343.

But after 4^3 they gave 10^2=100 so that one is odd one.

Siri said: (Apr 23, 2016)  
Perfect cube gives us the correct reason right?

Sanjay said: (Jul 19, 2016)  
5, 6, 14, 40, 89, 170, 291 find odd one in the given series.

Aman Soni said: (Aug 7, 2016)  
First of all we see the option in question is 27 100 125 343 in question said that find odd men out in option we see 27 125 343 these all are odd number then answer is 100.

Shambhu said: (Aug 30, 2016)  
The answer is 100 because it's not cube.

Monikavi said: (Jan 31, 2017)  
Logic : 2^3, 3^3, 4^3, 5^3, 6^3, 7^3.

So 100 is odd one.

Rushal said: (May 1, 2017)  
Thanks for all the given explanation.

Hari said: (Jun 12, 2017)  
1 3 6 11 20 39 70.

Diff-2 3 5 9 17 33.


=> Logic is x * 2-1 so 39 is wrong, replace with 37.

Meenakshi said: (Aug 19, 2017)  
8,27,64,100,125,216,343.

2^3 3^3 4^3 5^3 6^3 7^3 .
100 = 10^2.

Sonali Thilak said: (Sep 3, 2017)  
@Poornima.

You are right. Why can't we consider 343 as an answer guys?

Because that is the only prime no given there, right?

Akshay said: (Oct 4, 2017)  
Good one.

Aaron said: (Nov 25, 2017)  
343 is a prime number, why can't we consider that?

Subin said: (Apr 24, 2018)  
I thought it was 343 it is the only prime number in the series.

Mamatha said: (Jun 13, 2018)  
Thank you friends for explaining the logic of the answer.

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