Aptitude - Odd Man Out and Series - Discussion

It's about sequence as +2,+2,+1,+1,+2,+2,...So on

4+2=6
6+2=8
8+1=9
9+1=10
10+2=12......And so on
Hence there is no place for 11. So it is the odd one.

Here 11 is only the prime number in the numbers given above.

All other numbers 4, 6, 8, 10, 12 are divisible by 2, and number nine is divisible by 3 so these are not the prime numbers.

Hence, "11" is the odd one here.

11 is the prime number.

Here the logic is;

Consider 4,8,10 and 12. They are divisible by 2. Now consider 6,9 and 11. 6 and 9 are divisible by 3 but 11 can't be divided by 3.

So the answer is 11.

Why 9 is wrong answer? Please any one explain me.

{2*2=4, 4*1=4, 1*4=4}.....>.....4.

{3*2=6, 2*3=6, 6*1=6, 1*6=6}.....>.....6.

{4*2=8, 2*4=8, 8*1=8, 1*8=8}.....>.....8.

{3*3=9, 9*1=9, 1*9=9}.....>.....9.

{2*5=10, 5*2=10, 1*10=10, 10*1=10}.....>.....10.

{6*2=12, 2*6=12, 12*1=12, 1*12=12}.....>.....12.

All this no, have factors including factor of itself. Factor of it self i.e. [Example: 1*2, 2*1 ]. But only 11 in the option which has factors for itself we can't get 11 by multiplying with other no. s.

Its factor is {1*11, 11*1}.....>.....11.

This is the factors of 11. Now I hope Lavkush you may got atleast some idea why only 11 why not 9.

Number which are not prime is called composite numbers. 11 is prime number. Rest are composite numbers.

All numbers except prime numbers are known as composite numbers. Here 11 is a prime number so it is different.

I think 4 is divisible by 2.

6/3.
8/2.
9/3.
10/2.

11 is not divisible by 3.
12/2.

So 11 is odd man.

This is a flawed question. They should update it.

They use the word 'composite' to mean non-prime. Every number is either prime (divisible only by itself and one) or non-prime (having factors other than itself and one).

The question uses a sequence of natural numbers: 7 4 6 8 9 10 11 12.

They describe every number except 11 as 'composite' (having other factors apart from itself and one) but 7 is also in that category. So they made a mistake. End of story.