Aptitude - Odd Man Out and Series - Discussion

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!

It will definitely 73.

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 .

Hello in b/w 73 is there na. Why cant 73. ?

Number which is divide by itself and 1.

Explain what is prime number, I can't understand.

What is the prime number?

I Aree with vikash and vidya.

I agree with Vikash.

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.