Maths question - Civil Service is wrong (we now have 100% more threads about the subject)

[Sharingaroomtinightthen]

When I posted late last night I thought I’d get maybe half a dozen replies confirming the question didn’t have the correct answer and advising whether to tell the Civil Service recruiters. But here we are 1000 posts later.

https://www.mumsnet.com/talk/am_i_being_unreasonable/5384347-maths-test-to-think-civil-service-have-it-wrong

I have a maths degree.
I used algebra but could do it in my head.
It is not complex.

Disclaimer : I do teach maths but the students I teach are doing much more complex things than percentage difference.

Maybe there's something about it that's counterintuitive to some. At least one 'maths PhD' on the old thread insisted, I think, on 225. Perhaps a minor Monty Hall situation?

An application of Occams and Hanlons razors are problem the best approach here. More methodological rather than mathematical.

Agreed, the percentages are a red herring. You just need to assign values algebraically. However y, 2y, 3(2y) and 0.75(3(2y)) is less elegant than 100, 200, 600 and 450. The only time you need a percentage is (450-200)/200.

Perhaps the question "The circulation was 800,000, then it doubled ..." would have had a different response.

Yes.

(i) You are given two figures. One is 200, the next 450. What is the percentage increase?

(ii) Why is that missing from the answers?

The ability to turn words into equations - and more widely to use mathematics in an abstract manner - is key to almost all science and technology. I have no doubt that the intent of this question was to target those skills.

However, in a further example of natural laws, when trying to "be clever" the setters themselves committed a basic error.

If it does emerge that the answer is the question was mis-set, then it really does make me wonder what the hell is going on in Civil Service towers.

There is nothing counter intuitive about it.

It is a relatively simple percentage increase problem.

There isn’t. Maybe your friend just isn’t as accomplished as he’s led you to believe.

They have the qualifications to prove it. The original thread had accomplished mathematicians who also did not get the solution. The calculation is indeed extremely simple. Yet expert people get it wrong. That has got to be down to something in the wording.

It is indeed a trivial calculation. Another trivial calculation is to add up the number of professed experts on the threads who get it wrong. There must be a reason for this. My guess is that the wording is counterintuitive. What’s yours?

On second thoughts I make it 225% now, have I lost my mind? 😂 this thread is gold

Did they have sight of the multiple choice answers like the people on the original thread. Maybe it's more to do with faith in authority than the wording of the question itself?

Yes, I showed them the photo in the OP. They didn’t reach a conclusion, but gave a couple of answers at first sight and looked for a pen. I think writing the algebra down would have solved it. Perhaps they couldn’t see the wood for the trees (and we had had a couple of beers already). Though I got it at first sight, in my head, and I’m thick.

Did they also ask for the candidate guidance ?

"They" sound a bit full of themselves. You don't need to be a mathematician, to have circumnavigated the globe, to speak Mandarin and Icelandic, to have competed in the Olympics or to be a chess grandmaster to answer this simple question.

It's just some arithmetic mixed in with some pretty straightforward verbal reasoning.

No. Was there any in this case, according to the OP? I did see your (was it yours?) example of a test where those who didn’t listen failed by not hearing they didn’t have to answer everything. And I appreciate your posts about it perhaps being a bit more than just “Do this sum”.

That wasn’t my point. I agree it is simple arithmetic + straightforward reasoning. I did that myself off the bat, got the solution and realised the MCQ was mistaken. But several ‘experts’ on the threads got it wrong. My friend also had trouble seeing through it. Yes, it’s simple. But the presentation has something that foxes people it shouldn’t. I’m interested in why that is.

[Sorry for re-posting this. I forgot to “quote” your post to which I was replying]

No. Was there any in this case, according to the OP? I did see your (was it yours?) example of a test where those who didn’t listen failed by not hearing they didn’t have to answer everything. And I appreciate your posts about it perhaps being a bit more than just “Do this sum”.

Without the full guidance, it's hard to go beyond what seems to be a flawed test.

As I noted, when I had to take a serious screening test, the guidance explicitly said that you would not be able to answer all the questions. As I was told when I attended the follow up (for people who passed) that wasn't a challenge to try and psych the candidates out. It was a statement of fact they they were expected to verify and then address.

And it was the addressing they were testing. Not the maths.

Bottom line is if you towards the end of an MSc (or higher) in a technical subject, and you find a potential employer is testing your "maths" skills, then maybe - just maybe - you've missed the point.

Now whether or not that is the case here, we don't know. In the absence of further data, Hanlon reigns supreme.

Yes, Hanlon would explain the missing answer button being a mistake. One PP suggested they tweaked the question and forgot to check it still matched one of the answers. However, what explains the apparent difficulty, for some, in getting the correct answer?

One PP suggested they tweaked the question and forgot to check it still matched one of the answers

Given the obscene amount being spunked and planned on "AI" then that is unforgiveable and pretty much a resigning offence for whoever manages the civil service then. If there is no one in the civil service capable of running their entrance exam through a basic sanity check then the UK is doomed. (See also candidates who can't find "F7" ...)

I'd be really interested to see whether more people get it right without the multiple choice element.

It's very confusing and I think a silly way to express things. I always have to remind myself that a 100% increasing is doubling and work from there. I feel like once a week I find myself complaining to be husband: why doesn't the news article just say it "more than 8 times bigger" rather than " 707% bigger" or whatever silly % it is. I think very few people understand the latter.

Yes, you have.

End Y1 - this is the start point. Call it N (for Number).
End Y2 - 3N
End Y3 - 2.25N. This is the end point.

The increase in the end no. minus the start no., i.e. 2.25N minus N. The increase is therefore 1.25N.

The percentage increase is Increase / start no. * 100.
1.25N / N *100. This comes to 125%.

The problem is mathematically very simple. It's also easy to spout out the wrong answer if you've not read the question properly (ie it's increase from the end of y1, not from the start, and it's percentage increase, not percentage). A lot of people who skim read the question will get it wrong through carelessness, not lack of knowledge.

But the sheer number of people on this thread who were made aware of their mistake and still insisted they are right is ridiculous.