# Math Help - Complete the series

1. Originally Posted by ontherocks
1, 3, 13, 39, 89, ??

Options (183, 267, 359, 479) .

What I want to know is:-
Is there a way to solve such series if you don't know what the series is beforehand?
If the even terms are 3 times the previous odd term, then

$3(1)=3$

$3(13)=39$

$3(89)=267$

2. Very nice, AM. What's after that? Even to odd we have +10 and +50. Will you go with +90, +250, or something else?

3. Originally Posted by ontherocks
Exactly. Thats what generally happens and was exactly my point in all these ramblings.
But what can you do about it? Either you have somehow find "his" answer from "his" options or get no marks and get out.
That, my friend, is an excellent question. You have waded well through a rather difficult social discussion. Unfortunately, there is no clear answer. It is rather a question of morality.

Personally, I committed to myself early on that I would LEARN from my studies and not EVER play the "guess what someone wants" game. This started early for me. I can suggest very specific examples from as far back as 2nd grade where I challenged the established authority on what it was they were trying to do and whether their methods were appropriate. (Okay, I was rather a freak.) In ALL possible cases, I have challenged the unfair problems with multiple solutions - sometimes deliberately incorrect. In cases where I could have little influence, I sometimes just took my lumps. This can be difficult, realizing and accepting that one is not in control of one's own life and that the errors of others can mess with us. Again, for me, I choose to go with personal integrity rather than bowing to the system. Most often, those I challenged were delighted to have the challenge. I have found the same to be true in the other direction. Those that challenge me either teach me something new and I change my views or the challenge provides for me an opportunity to strengthen my original position.

Apptitude exams are tricky. One must question what aptitudes are being challenged. It is not always clear.

Placement exams are very tricky. Most want to do well on them. That's a bit odd as it is intended for placement. One should do as well as one can. One should not perform over one's actual current ability.

Note 1: The Society of Actuaries went through some growing pains not too long ago. They completely discarded a certain question type from their syllabus. They received enough complaints and the discussion was of sufficient strength that they decided simply never to write such a question again. This is excellent evidence that those in authority can be persuaded.

Note 2: I could not find documentation for it, but I recall a single high school student some years ago rather embarrassing one of the big college entrance exam folks. In a 3 Dimensional geometry problem, the student proved that the exam committee was simply wrong. The committee ate their error and gave a higher score. This is excellent evidence that those in authority are not necessarily tyrants.

Well, that's quite a bit of discussion over the five seemingly-harmless numbers where we started!

4. Originally Posted by TKHunny
Very nice, AM. What's after that? Even to odd we have +10 and +50. Will you go with +90, +250, or somehting else?
It's not part of the OP's question.

5. Originally Posted by Archie Meade
If the even terms are 3 times the previous odd term, then

$3(1)=3$

$3(13)=39$

$3(89)=267$
I like that. Nice indeed

6. Originally Posted by ontherocks
1, 3, 13, 39, 89, ??

Options (183, 267, 359, 479) .