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

@ItsFineReally That is not correct the increase in circulation from

200 to 600 is a 400 increase in circulation which represents a 300% increase this means the final answer must be above 300%

Next year circulation decreases by 25% so 400-100=300

300 is an increase of 150% from the starting point of 200 so

300% plus 150% is a 450% increase

The correct answer is 450%

Read all my other examples it may help you understand no matter what number you give me it always works out at 450% as the answer. You gave me 8 saying it would never work but it does.

The answer is 450%

Read all my other examples the maths works and the answer is 450%

@Spiderbitebatbite Which bit isn't correct? I've simply asked you to clarify what you think the figures are. You agreed you have:
200
600
300
You agree the original question asks for the percentage increase in the figures?

I've then questioned why you think the increase from Yr 1 to Yr 3 (which is the original question) of 200 to 300 can be 450%.

I've not tried to give you a different explanation, simply step through your own calculation.

Ok, you are trolling now. I'm out.

There is so much wrong here that it’s impossible to know where to begin.

@ItsFineReally with my calculation I do not agree that the question asks you to calculate the start point and end point without also fracturing in the trebling 300% increase in between. This is why the answer must be above 300%.

200 to 600 is a 400 increase in circulation which represents a 300% increase this means the final answer must be above 300%

Next year circulation decreases by 25% so 400-100=300
300 is an increase of 150% from the starting point of 200 so

300% plus 150% is a 450% increase

The correct answer is 450%

I thought I'd give it a bash from a different angle and ignore the rest. But alas. 🤷‍♀️

Sigh.

This is fascinating to me @Spiderbitebatbite

Why are you using the circulation increase as the thing that is reduced by 25%? It should be the 600 that is reduced by 25%, no?

Separately, as has been shown, tripling is not a 300% increase.

Are you a chatbot designed to infuriate and avoid engaging with the questions people pose to help you identify the issues with your logic?

Say Potato, @Spiderbitebatbite !

You are being baited by the spider. Relax.

And I thought the 225% people on the other thread were bad - they've got nothing on the 450%. You can't just declare that tripling represents a 300% increase because it does not.

😂

Thanks for doing a thread 2, OP.

Somewhere right now...

You have £100 in the bank.

After 1 week, you have £300 - a nice increase!

But, the next week, you lose £75.

According to our spider friend, losing that money actually results in a bigger total increase.

Thanks for giving us something to work with, @Spiderbitebatbite . So, line by line;

200 to 600 is the trebling from the end of Y1 to the of Y2, an increase of 400. Agreed

But an increase of 400 is only an increase of 200% from the end of Y1 to the end of Y2. You said it was a 300% increase. (If you count from the beginning of Y1, which we all agree is wrong anyway, it is a 400% increase). Disagree here

Next year, Y3, the circulation decreases by 25%.

You use 400-100=300. I use the Y2 end figure of 600 and subtract 25%, so

600-150=450, for a Y3 end figure of 450. Disagree

So end Y1: 200. End Y3: 450.

(450-200)/200= 250/200=1.25

Amount at end of Y3 is 225% the amount at end of Y1 and the increase is 125%.

PS, when I say ‘Disagree’ I am being polite. Academics use this form to point out mistakes of fact as I have done above, as well as genuine differences of opinion.

If anyone wants to pursue a difference with me on the points I have isolated, they need to explain why @Spiderbitebatbite ’s computations rather than those usef by PPs and me model the situation correctly. Not just repeat @Spiderbitebatbite ‘s computation’s but explain why they model the situation correctly.

@Spiderbitebatbite

I'm afraid you are making yourself look very silly.

You seem to be under the impression that doubling a number increases it by 200%. It doesn’t. It increases it by 100%, i.e. the same again.

If your salary doubles, the new salary total is 200% the size of the old total - but the % increase is 100%.

Saying that because the total trebles at one point in the calculation (before falling again anyway) means it must increase by more than 300% is illogical and just incorrect.

😂😂😂 this is gold!

If you’re a troll then you’re a genius!

If you genuinely think this is how maths works then I fear for how you get by in life 🤣

Spidy is the Bgassfraudfruad fella from the previous thread. Both are magnificent trolls.

You've missed a step in calculating the change.

it's (1x3x0.75)-1

i.e. It's the increase (2.25) minus the original (1)

Trebling a number is a 200% increase. Treble 1 and you get three. That is an increase of 2, not 3.

I'm a bit worried. My boss has said my pay will soon be increasing by 10%. I was happy because I thought this meant it would go from £50k to £55k. But according to spidermaths it looks like it'll be actually be going to £5k. Do I need to ask for a 110% increase to get from £50k to £55k?

That’s not how percentages work 😂

I read those workings again and honestly thought I might be having a stroke.

It takes quite a talent to wholly fudge a problem so very comprehensively.