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

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.

There is nothing counter intuitive about it.

It is a relatively simple percentage increase problem.

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.

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?

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.

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

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?

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.

It is strange. I am only of average intelligence, not advanced in maths, but 'saw' it straight away.

Are you American ?

In the quantum theory of multiverse maybe there is a universe where the answer is 225%?

There are plenty of "subtle" tests that are not what they seem. Or that can deliverer .... interesting results.

Any "Taskmaster" fans reading ?

That's so strange. I gave it to my 12 year old, fairly average at math, son and he got the right answer in his head. It's really not complex.

@BrickBiscuit @DadDadDad @TeenToTwenties @RedDoorBlueHouse

Thanks all! I’ve been contemplating your replies. It has taken a few days of thinking (literally…), but I think I finally understand. I wasn’t sure how you determined the methodology to answer the question; I think I found it confusing to know how to answer it because the question refers to percentages, which sound like (from the wording) each increase (doubling then trebling) is its own little individual percentage packet, if that makes sense, but the methodology to find the answer is more like using algebra (in my head, anyway).

Another confirmation, perhaps, that I should stick to my day job! 😂

Thanks again.

@SerendipityJane I showed this to a mathematician friend. They are also a multilinguist, high level chess player, sportsman and much travelled (don't worry - face like a potato and likes Trump). The wording was genuinely puzzling to them, and they didn't reach a definitive conclusion yet. They immediately went to algebra. We didn't have a pen handy, and that was their first request. I think there is something about the wording, maybe lots going on at once, that makes a simple calculation seem complex.

@Supperlite sorry for being careless, but I should have said 'no point calling them all proportions of A' in my previous reply (instead of 'calling them all A').

You are over-complicating it. You have a figure at the end year 1, year 2 and year 3. They are all different, so no point calling them all 'A'. Taking the start of year 1 as 100%, the figures are 200%, 600% and 450%. You are asked for the percentage increase from 200 to 450. 450-200 (that's 250, the difference between them) is 125% of 200.

YABU for starting a new thread. You are just showing off now OP 😂

My DH who has a maths degree and works in finance initially said 225. I, who is fine with day to day maths but only has a lowly C grade GCSE, said 125. DH then looked at it again and admitted I was right 😂

I asked 2 maths teachers. One said 50% and the other said 450%. I asked the 2nd one to rtfq and he cane back with 125% 🤣

I wanted to try and point out exactly where you went slightly wrong.

Year 3-4 reduces A by a quarter of A.
A is 200% (A is NOT 200% at this point, in your last point you said A has just had a 200% INCREASE (tripling), which was preceded by a 100% INCREASE (doubling) . This means A is now 600% of its original value, so reducing by quarter will take it to 450% of its original value)

And the question is what is the increase between the time when A is 200% of its original value and when it is 450% of its original value.

200% to 450% is a 125% INCREASE.

@poetryandwine @niadainud

I think the ‘start at 50’ comes from me. A lot of posters were saying ‘imagine at the end of the first year you have 100’ so I said ‘imagine at the end of the first year you have 50’ because you then start the sum by doubling it, ie you now start with 100. In trying to make it simpler for people to understand, I thought 100 was a nice easy number and easier to visualise.

But it went fecking wrong. Again.

Yes, it’s 125%.

I know there are no ‘numbers’ in the question, it is just easier for some people to have actual numbers.

Unfortunately there are 2 threads, in which roughly 80 of posters have been extremely keen to demonstrate just how poor their comprehension, mathematics and understanding of percentages is 😂 But, the answer is 125%, which is not one of the answers available. Which is where this all started 😊

real life doesn't always have check boxes 😀it's a philosophical point.