Tuesday, February 24, 2009

What's the answer?

Numerical reasoning

Question;

5/3 is to 1/5 as 5 is to ?


Leave a reply even if it matches someone else.
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14 comments:

Anonymous said...

I never liked maths, but I will take a stab at it, my guess is 8.

2:25 PM
Anonymous said...

3/5

i knew I would use that B.Sc. one day!

2:56 PM
Anonymous said...

ropata is correct

5:47 PM
mojo said...

Yep, Ropata is.

7:12 PM
bruddah said...

5 was obtained by multiplying everything by 3.

hence 5/3 becomes 5
and 1/5 becomes 3/5

The question isn't mathematical reasoning so much as ability to parse confusing pseudo-mathematical sentences.

Mathematical reasoning is a rigorous form of deduction and proof, it's within the grasp of most people but the way it's taught puts people off. All those symbols and deliberately misleading questions like the example above. People can learn to enjoy puzzles and problem solving if they are taught strategies and experience success.

7:47 PM
Anonymous said...

3/5 is a possible answer.

So is 3 8/15 (or 53/15).

So is 1/15.

The question doesn't contain enough information to require a unique answer.

Dave Christian

11:04 AM
Anonymous said...

So is -1/5.

I suspect that there are an infinite number of solutions.

Dave Christian

11:22 AM
Lindsay Mitchell said...

I get your reasoning Ropata. I turned the fractions into 30ths and now come up with 18/30 - same as 3/5.

The question is actually from the police recruiting test which I have filled in again trying to win their monthly I-pod prize.

http://www.newcops.co.nz/GetStarted/TakeTheTest


This is the only one I got wrong by initially answering one. I said in my head five thirds is to a fifth as 5 is to one. And I still think that's an option.

I can also follow your reasoning Dave.

What's the lesson in this? That the cops see things as black and white when they are not? That there is only one possible culprit when there are several? :-))

12:01 PM
Anonymous said...

The lesson is that thinking logically is no longer valued in schools.

My kids went through college back in the bursary days and were often told that the obvious answer was the right answer and that less obvious - but perfectly correct - answers were "wrong".

Actually I could put up a strong case that the first two alternate answers I gave are superior to 3/5, but I'm sure that you don't want to hear such pedantic didacticism.

1:00 PM
Anonymous said...

The answer is 1, isn't it?

Finding 15 as common denominator then the original numbers are 25/15and 5/15 five to one ratio). So, in the second case 5 must be followed by 1.

2:40 PM
Lindsay Mitchell said...

Except 1/5 is not 5/15 ...

3:21 PM
Anonymous said...

My misatke. The answer would be 2/3 then.

3:30 PM
Anonymous said...

If you do these sort of tests often enough you understand what the hell they are talking about, so 3/5 is the only 'correct' answer. Convert the shitty fractions into decimal numbers, it's just scaling a ratio of numbers. Boils down to understanding the rules of the game and a few numerical tricks. I suppose cops need a basic grasp of logic, numeracy, reading comprehension, but it still seems like a trick question.

A few different ways of looking at the problem:

The ratio 5/3 : 1/5
== 25/15 : 3/15
== 1.6667 : 0.2

Scaled up by factor of fifteen ==> 25 : 3
Scaled up by factor of three ==> 5 : 3/5

4:55 AM
Anonymous said...

"If you do these sort of tests often enough you understand what the hell they are talking about".

Quite. Rote 'learning' is in and thinking is out.

Only when we consign state education to the pages of history books will more than a small minority of people again aquire thinking skills.

Dave Christian

2:51 PM

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