Aptitude - Odd Man Out and Series - Discussion

Addition of prime number to previous digit.

3, 5, 7, 9, 11, 13.

Odd place even no, even place odd no. But 64 is even.

Its very simple just follow this, just go on subtracting.

2, 5, 10, 17, 26, 37, 50, 64.

5-2=3.
10-5=5.
17-10=7.
26-17=9.
37-26=11.
50-37=13.

But 64-50 is equal to 14. We have seen that the order is 3, 5, 7, 9, 11, 13.

All are odd numbers but 14 is an even number. So finally the answer is 64.

The answer can be solved out in two ways:

1) The series is continued by first squaring the numbers from 1 and then next we have to add one the squared numbers and so on. By which 64 is the only number in the series written without adding 1 to it after squared.

2) We can also solve in the another way. Add the subsequent odd numbers from 3 to the given series but we find 65 is obtained in place of 65 by adding 15 to 50.

Therefore it can be judged that 64 is the odd man out.

37 can be the right answer because it is odd digit.

The difference between the numbers are prime except between 50 and 64.

5-2=3.
10-5=5.
17-10=7.
26-17=9.
37-26=11.
50-37=13.
64-50=14.

3, 5, 7, 9, 11, 13 are prime numbers but 14 is not. So the answer is 64.

also series that is obtained after subtracting evry proceeding no. from the previous increases by two

general term :
tn = t(n-1) + 2n-1 where n = 2,3,4,5...
t= 2
t1= 2 + 2(2)-1 = 5
t2= 5 + 2(3)-1 = 10
t3= 10 + 2(4)-1 = 17.... and so on where 64 is out of pattern

Here we can easily subtract the 2 numbers and the difference should be ordered by 3, 5, 7, 9, 11, 13, 15, 17. Like that'but the number 64 is exempted from this case.

1+3=5
5+5=10
10+7=17
17+9=26
26+11=37
37+13=50
50+15=65 not 64...
(3-5-7-9-11-13-15) 64 is odd