Aptitude - Odd Man Out and Series - Discussion

Find the odd man out.

13. 

41, 43, 47, 53, 61, 71, 73, 81

[A]. 61
[B]. 71
[C]. 73
[D]. 81

Answer: Option D

Explanation:

Each of the numbers except 81 is a prime number.

Ankita Sood said: (Aug 28, 2010)  
General term is

tn=t(n-1)+2n ,where n is 1,2,3..

t = 41

t1= 41+2(1) = 43
t2= 43+2(2) = 47
t3= 47+2(3) = 53... and so on where 81 doesn't fit into the series.

Vikash said: (Mar 15, 2011)  
Ya dude you are right

41+2=43
43+4=47
47+6=53
53+8=61
61+10=71
71+12=83

So 81 doesn't fit in the series.

Vidya said: (Apr 27, 2011)  
I agree with Vikash.

Mythilee Velu said: (Jun 29, 2011)  
I Aree with vikash and vidya.

Asha said: (Aug 10, 2011)  
What is the prime number?

Asha said: (Aug 10, 2011)  
Explain what is prime number, I can't understand.

Karthi said: (Aug 12, 2011)  
Number which is divide by itself and 1.

Chand said: (Aug 14, 2011)  
Hello in b/w 73 is there na. Why cant 73. ?

Sandeep said: (Aug 21, 2011)  
I didn't understand
when n=1
then t1=41(1-1)+2(1)
=41(0)+2
=0+2
then t1=2
then how come t1=43?

Please explain .

Aran said: (Sep 10, 2011)  
It will definitely 73.

Sh3 said: (Sep 21, 2011)  
81 is divisible by 9, so it isn't a prime number. 9x9=81. the rest of the numbers can not be divided into evenly without a remainder. For example 5 is a prime because if you divide it by 2 you will have a remainder. 5 is only divisible by 5 or by 1.

also stated above was the formula: tn= t(n-1)+2n
where n= 1,2,3,4,...etc.
and t= 41,43,47,53,...etc.

If you plug in the numbers it doesn't equal the 2nd term which is 43.
let t= 1st term 41
n= 1

Example with above formula:tn= 41(1-1)+2(1)
41(0)+2 = 2?
I do understand t+2n
41+2(1)= 43
43+2(2)= 47
47+2(3)= 53

I am not trying to be picky, I was really trying to understand.
thanks for the above solutions!

Sunitha said: (Oct 21, 2011)  
Thank you ankita.

Shantanu said: (Nov 11, 2011)  
Hey people it should be 73 also..... because in each case 2 is getting added and in that case 73 doesn't fit!!

Saurabh said: (Nov 27, 2011)  
What is prime no?

Yogesh Rai said: (Dec 5, 2011)  
4*10+1, 7*6+1, 6*8-1, 6*9-1, 6*10+1, 7*10+1, 8*9+1,
but there are 9*9= 81

Praveen said: (Feb 21, 2012)  
I am not agree with Vikash and ankita as according to them 73 and 81 both will be the answer.But we have to choose one answer.So correct answer is 81 which is not a prime number

Ikram said: (Mar 9, 2012)  
I agree with praveen.

Raju said: (Apr 26, 2012)  
Hey how you express above formula in to the sum. tn=t (n-1) +2n.
For example =41 (1-1) +2*1=2.

Paresh said: (May 7, 2012)  
41+2=43.
43+4=47.
47+6=53.
53+8=61.
61+10=71.
71+2=73.
73+4=77.
But there is 83, which was not in same sequence. There must be 77.

Imran Parvez said: (Jul 28, 2012)  
A number which is divisible by one (i.e 1) and itself (the same number that is given) is called a prime number.

Sandeep said: (Aug 10, 2012)  
Hai friends any can say an easy steps to find like this oddman out problems.

Raja said: (Apr 29, 2013)  
To find odd man out series, we are using five procedures.
Those are,

1) Check the sequence is any cubes or squares.

2) To find the relation b/w two following numbers.

3) Any relation b/w the given number like,
Adding or multiply last two get the first digit.
Adding or multiply first two digits get the last digit.
Adding or multiply first and last digit get middle one.

4) That is prime numbers or not.

5) Those numbers are odd or even.

Mostly these types are using formed the odd man out series.

Jyoti said: (Jul 30, 2013)  
81 is not a prime number but it is a perfect square.

Akshay said: (Sep 10, 2013)  
The prediction is right since,

I too tried by the logic such as:

41+2 = 43.
43+4 = 47.
47+6 = 53.
53+8 = 61.
61+10 = 71........71+2 = 73.

In this case when multiplier become 12 then the logic is violated so if we follow this prediction the answer should be 73, so I think this not proper prediction, and the prediction that mentioned in the key even proper than this.
So that is the pragmatic logic.

Sourabh said: (Jan 6, 2014)  
41, 43, 47, 53, 61, 71, 73, 81.

Difference b/w to number is even series..

43-41 = 2.
47-43 = 4.
53-47 = 6.
61-53 = 8.
71-61 = 10.
73-71 = 12.
81-73 = 9 its wrong so answer is (D).

Billa said: (Jul 31, 2014)  
@Soourabh.

73-71=12?
Can you explain it?

K.Jahnavi said: (Sep 10, 2014)  
41, 43, 47, 53, 61, 71, 73, 81.
The difference b/w two numbers is even series. i.e, 2,4,6,8,10.

But 73-71 = 2.
So we can get 73 as wrong number of the series.

Snigdha said: (Sep 18, 2014)  
73 is wrong in the series according to me. 2 is getting added.

Sam said: (Sep 27, 2014)  
Answer is 73 not 81, But 81 should be 83.

Jinendra said: (Nov 2, 2014)  
81 is not a prime number.

A prime number is which is divisible by 2 or itself & in this case 81 (9x9 = 81) and the answer is 73 okay.

Kishore said: (Jun 23, 2015)  
Except 81 is multiplied wit 9 & other numbers can be multiplied by itself.

Murali said: (Aug 7, 2015)  
All the numbers are prime numbers except 81.

Prime number series is 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499, 503, 509, 521, 523, 541, 547, 557, 563, 569, 571, 577, 587, 593, 599, 601, 607, 613, 617, 619, 631, 641, 643, 647, 653, 659, 661, 673, 677, 683, 691, 701, 709, 719, 727, 733, 739, 743, 751, 757, 761, 769, 773, 787, 797, 809, 811, 821, 823, 827, 829, 839, 853, 857, 859, 863, 877, 881, 883, 887, 907, 911, 919, 929, 937, 941, 947, 953, 967, 971, 977, 983, 991, 997 etc.

Imran said: (Apr 24, 2016)  
3, 13, 31, 58, 91, 111 choose the wrong number in the series.

a) 58 b) 31 c) 91 d) 111.

Can anyone help me to solve this problem?

Amit said: (May 5, 2016)  
t = 41 + 2 * 1 = 43
t = 43 + 2 * 2 = 47
t = 47 + 2 * 3 = 53
t = 53 + 2 * 4 = 61
t = 61 + 2 * 5 = 71
t = 71 + 2 * 6 = 83.

In the given Series there 73 followed by 71, so the answer must be 73.

Sandeep Shenoy said: (Jun 10, 2016)  
Answer 81 is correct. Because except 81, all other numbers are a prime number.

Lakshman said: (Jun 26, 2016)  
Yes, I agree with Sandeep Shenoy.

Manav said: (Jul 1, 2016)  
Why its ans can't be 47?

41 4>1
43 4>3
47 4<7
53 5>3
61 6>1
71 7>1
73 7>3
81 8>1

Every 10th digit no is more than except 47, so the answer is 47. Why this answer is wrong?

Tanmoy said: (Aug 15, 2016)  
BUT why not 73 because its also not fit in series with 81? both are not fit isn't it?

Sunil said: (Sep 18, 2016)  
If we solve like that:
43 - 41 = 2,
47 - 43 = 4,
53 - 47 = 6,
61 - 53 = 8,
71 - 61 = 10,
73 - 71 = 2.

So, that 73 makes an error for the exact difference between the given numbers so according to me, 73 is an answer .

Neha Sultan said: (Nov 21, 2016)  
It's 81.

That's because NO OTHER NUMBER IS PERFECTLY DIVISIBLE BY 3, EXCEPT 81.

Vijayalakshmi said: (Aug 1, 2017)  
What is a prime no?

@Murali.

How did you wrote the series of prime no. Can you explain it?

Karthika said: (Aug 15, 2017)  
I think the answer is 73.

Amandeep said: (Aug 17, 2017)  
81 is right because no any number in the series divide by any number.
only 81 divide with 3,
27.

Mukesh Yadav said: (Sep 8, 2017)  
Yes, I agree @Karthika.

Sarukh said: (Sep 16, 2017)  
They all are prime no except 81. So simply 81is the perfect solution.

Bunny said: (Oct 5, 2017)  
Yes, @Amit is right answer 73.

Abhay Raj said: (Jan 25, 2018)  
41+2 = 43.
43+4 = 47.
47+6 = 53.
53+8 = 61.
61+10 = 71.

So 81 is not correct.

Vimala said: (Jul 19, 2018)  
81 is the only number divisible by 3.

Raja Ram Choudhary said: (Aug 1, 2018)  
@Saurabh.

A number that is divisible only by itself and 1, then we are called prime number.

Kiran Dudi said: (May 20, 2019)  
Why not 73?

Arjun Tejaswi.S said: (Jul 22, 2019)  
It can be solved in this way too.

41+(1*1)+1 = 43
43+(2*1)+2 = 47
47+(3*1)+3 = 53
53+(4*1)+4 = 61
61+(5*1)+5 = 71
71+(6*1)+6 = 83.

And here 81. So, therefore, it is out of the series.

Abhi said: (Sep 13, 2019)  
81 is the only one which is divisible by 3.

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