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

But how would the student record their answer?

Maybe that's the ingenuity test ?

Similar to "How can I answer this absolute bollocks question about my gender identity because there isn't a "What is this nonsense ?" option.

Who knows, by having the cojones to make this a long running series of threads on the UK premier parenting and right wing woke captured platform, maybe the OP will receive a tasty offer on Monday ?

You have made an error with your "start figure". We need the figure at the end of Y1, when it has already doubled, not the "original" figure from the start of Y1.

Original start no - 100
End of Y1 (after doubling during the year and reaching our start date) - 200
End of Y2 - 600
End of Y3 - 450

The change (increase) is 250 but you have put your start figure as 100 when it should be 200.

250/200 * 100 (to give us a % change from end Y1 to end Y3) = 125%.

So with your example, the question is how much has 20 increased by in percentage terms to get to 45?

The answer is 100% to double to 40 plus another 25% (5)

Meaning the answer is 125%. The test setter messed up

https://www.studiosity.com/student-resources/practice-tests/year-7-general-maths-practice

I think everyone commenting anything other than 125% should take this test and see how they do before being so wrong and strong.

I'd have gone for 150%. Increase in percentage from y1 to y2 is 200% (3x-x=2x). Then it drops by 1/4 (200/4=50). 200-50=150. But having read the answers I got confused and am now seriously doubting my maths ability.

You beat me to it!

Turns out there was no point anyway as people are still arguing about it 😂

It's not the percentage increase that drops by 1/4 though, but the actual circulation value at that point (so in your example, 3/4x). Your 2x-3/4x is 1.25x, which is 125% if you express as a percentage.

Let’s dumb this right down.

Imagine there is no change between Year 1 and year 3. Obviously the percentage increase is zero, nothing has changed.

It would remain 100% of the original figure - no more and no less.

But there is no increase. Nothing. Nada. 0%.

So Y3 would be 100% of Y1. It would also be a 0% increase.

I wondered if this was because your post had got buried in the middle of the thread. However the calculator is now right at the front of the thread and people are still arguing the toss .

So, it turns out you were right, and people just aren't very truth-seeking. Absolutely fascinating.

It really is. I find it really interesting as well as despair-inducing.

I just asked my husband about it. He misunderstood, got it wrong. I explained. He realised. Easy.

It’s not the misunderstanding or the getting it wrong I find hideous - it’s the refusal to be taught.

Many correct calculations for the problem as it was posed have been given. The answer is indeed 125%.

There is no ambiguity.

I agree with the conjecture that the problem was tweaked during a review of the exam and the answer key was not adjusted.

Good on you, OP, for defending your position so well. If I had to do with hiring in the CS I would take under advisement the impressive way you’ve done this.

STEM PhD here

STEM PhD here

No-mark thicko here. Not a STEM qualification in sight, and even I can see it’s 125%.

Absolutely agree - there’s no ambiguity in the question. It’s so simple, once you’ve read it carefully enough, and I can’t understand how so many are getting it wrong.

Which is 125%

Not 225%
Not 450%
Not any other %
Not a great screen of drivel copied and pasted from ChatGPT that concludes some other number

125%

It's not hard and it's not a badly written question. Jeez.

I think the fact that year 3 is 450 confused people.

If the number at the end of year 3 were 400 (as opposed to 450), then it would be simple. 400 is double 200 , so that’s a 100% increase.

Now deal with the 50. That constitutes 25% increase from 200

So it’s 125%

Why are you quoting me? I’ve been #team125 from the start…

I wonder if the publicity from these threads might boost the circulation of News Today. I’m certainly buying it tomorrow. They might sell an extra copy for every two they sold previously. That’s half as much again, or a percentage increase of 50%.

Wish we still had the smile icon for a reaction icon.

I’m afraid you’re going to have to recalculate your thread title…
https://www.mumsnet.com/talk/am_i_being_unreasonable/5384837-maths-skills?utm_campaign=thread&utm_medium=app_share

I’m just trolling you sorry 😂😂

100

200
600
300

As the question states starting from 200 after the 100 is doubled.

Treble Increase from 200 to 600 is 400 which represents 300% increase in year 2.

25% decrease in year 3 so 400 minus 25 % is 300 which is an increase of 150% from year 2 starting point of 200.

300% plus 150 % equals 450%

You can use any number with my logic above and it always comes out as 450%.

200

400
1200
1000

As the question states starting from 400 after the 200 is doubled

Treble increase of 800 which represents the 300% increase in year 2.

25% less of 1200 total increase in year 3 so 1000 which is an increase of 150% starting point of 400.

Again 300% plus 150% is a total of 450% increase.

IMO the question clearly states the numbers in circulation trebled so the answer has to be above 300% anyway. When calculating the final increase accounting for a 25% decrease the answer is 300% plus 150% which is 450% which, conveniently for me I would have chosen and got right.

All you who keep spouting 125% is the right answer are wrong maybe that’s why there isn’t an option for it! You all remind me of sheep to the slaughter!

That's possible. Could be to see who will comment that the correct answer isn't on offer. I remember during an aural exam in French A level, the multiple choice answers for qu 11 and qu 12 were the wrong way round. I listened to qu 11 and the answers didn't make sense. My French teacher didn't look confused. No one else in the room looked confused. Then the next question was played and it was clear the options for it and the previous question had been mixed up. I made a note of it and told my teacher. He seemed a bit surprised but checked and realised it was a mistake and contacted the exam board who told him no one else had noticed. I bet they had. I bet loads of people had. But they hadn't wanted to make a fuss.

I tried to follow your method @Truelyscrumptious21 but my brain got confused so I put it into Gemini - this is the result I got:

Thank you for sharing that perspective. I understand the frustration you feel when an answer that seems logical to you is challenged by others, and I will do my best to explain why this approach is not mathematically sound.
Your analysis is creative, and it attempts to account for a change in scale, which is an important concept. However, the method you've used is based on a fundamental misunderstanding of how percentages work in this context.
Here's a breakdown of the flaw in the argument:

The Value of 1%

Your core premise is that "1 newspaper equals 1%" at the start, and that this value changes. While it's true that 1% of 100 is 1, and 1% of 200 is 2, you cannot use these numbers as a separate metric to calculate an increase. The value of 1% is always tied to a specific base number.

• When the circulation is 200, 1% of it is indeed 2.
• When the circulation is 450, 1% of it is indeed 4.5.

But you cannot subtract these values (4.5 - 2) to get a new percentage. That calculation is comparing two unrelated values (1% of 450 vs. 1% of 200) and combining them in a way that has no mathematical meaning.

The Correct Way to Account for Scaling

The standard percentage increase formula already accounts for the change in scale. The formula is designed to use the starting value as the base for the entire calculation.

• You start at 200 newspapers (at the end of year 1). This is your 100% baseline.
• You end at 450 newspapers (at the end of year 3).

The increase is 250 newspapers. The question asks what percentage this increase of 250 represents of the original value (200).

Your own calculation (4.5 newspapers equals 1%...) incorrectly creates a new and complex way to measure the change, but the final answer you arrive at (450%) is not supported by any known mathematical principle.

Your Final Calculation

The final step of your calculation (450/250= 1.8 x 2.5= 4.5 x 100 = 450%) is also incorrect. There is no logical or mathematical reason to perform these specific operations in this order.

The correct and universally accepted way to calculate a percentage increase is:

1. Identify the original value (200).
2. Identify the new value (450).
3. Calculate the change: 450−200=250.
4. Divide the change by the original value: 200250=1.25.
5. Multiply by 100 to get the percentage: 1.25×100=125%.

The answer is, and will always be, 125% based on the standard rules of mathematics. While your effort to find a different solution is commendable, it is based on a flawed premise about how percentages work. The previous posters who arrived at 125% were not being dictatorial; they were simply using the correct and established mathematical method for solving the problem.

@Spiderbitebatbite Just to start with,

Treble Increase from 200 to 600 is 400 which represents 300% increase in year 2.

Going from 200 to 600, or trebling the original 200, works as follows:
You start with 200, your starting value. You have 100% of 200. You add 400. 400 is 200% of 200. You have added 200% of the starting value. You have increased it by 200%. This makes a total of 600, which is 300% of your starting value. But the increase has been 200%. Total = 300% and increase = 200% of the starting value.

The rest should follow.