### Brain Teasers

# 4.5, 4.5, 12.5, What?

Series
Series teasers are where you try to complete the sequence of a series of letters, numbers or objects.

A teacher got mad at a student, and gave him one last chance to see if he was paying attention. "You'll give me a number and I'll give you one back, and you must find out the rule. You only get five numbers! Once you get one wrong, you will get detention immediately!"

Here is a summary of what the student said and how the teacher replied.

Input 1 , 2 , 3 , 4, 5

Output 4.5, 4.5, 12.5, 8, 8

What is the rule?

Here is a summary of what the student said and how the teacher replied.

Input 1 , 2 , 3 , 4, 5

Output 4.5, 4.5, 12.5, 8, 8

What is the rule?

### Hint

It's not really a rule...### Answer

The rule is to count the number of letters of the number, square it, then divide by two. So:1 = 3

2 = 3

3 = 5

4 = 4

5 = 4

(3^2)/2 = 9/2 = 4.5

(3^2)/2 = 9/2 = 4.5

(5^2)/2 = 25/2 = 12.5

(4^2)/2 = 16/2 = 8

(4^2)/2 = 16/2 = 8

Luckily, that student didn't get detention because of his quick wit, but who knows if he will be lucky next time...

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## Comments

Whoa! Complicated quiz time!

Well, I guess I am not that witty student. Very creative, and hard! I would have never thought of that.

WOW, nice one, it was hard, but i got it my first try. I guess i wouldn't have a detention.

Okay, I totally did not get that one.

Lol, I didn't get it either, and I voted to reject it because it was too trivial for me

I thought I had the right idea (it seemed obviously to do with counting the letters and dividing by 2), until I saw the hint, which seemed to indicate there was no mathematical relation. If it had said "It isn't really a sequence" I could understand. Good one, otherwise.

Good one. I didn't get it. That's one tough teacher!

Tricky

easy...fun...

Great teaser. Why aren't you posting teasers anymore? You have such good ones.

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