There is a logical pattern to the following series of numbers. What are the next three numbers in the series?

15 21 25 27 33 35 39 ...

The next 3 numbers are - 45, 45, 51

I'm not too sure of this. I just looked at the factors of each number in the series and noted a kind of progression there and used that.

For the series
15 21 25 27 33 35 39

the factors are -
3,5
3,7
5,5
3,9
3,11
5,7
3,13

The cofactor with the 3 in all the cases is in an AP (arithmetic progression) interrupted every 2 steps by a 5,something.

the 5,something has the something in progression as well.

So we get the answer.

Posted by Anoop on 2003-02-10 03:11:11