Maths test - to think Civil Service have it wrong?

[Sharingaroomtinightthen]

I’ve just applied for a Civil Service test. Part of it is passing a numerical test.

This is the question.

The answer is 125%. I’m sure of it.

If you start with £100, and in the first year it doubles it’s £200. So at the of year one it’s £200.

In year two it trebles to £600.

It then falls by a quarter in the third year to £450.

So end of year 1 - £200.

End of year 3 - £450.

It’s increased by 125%.

125% isn’t an answer option.

WIBU to email and tell them they’ve got it wrong?

So 200 to 450 is a x225% increase.

No it is not. 200 increased by 225% is 650.

I wonder what people think when inflation is 4%

I think the increase is 500%.

They’ve been quite shifty with the wording. It reads ‘in one year the circulation doubled’ rather than in year 1. So, using your 100 example, won’t it be:
year 1 - 100
year 2 - 200
year 3 - 600
yeat 4 - 450
With the percentage increase between the end of year 1 and the end of year 3 being 500%?

Not if you insert numbers in the equation.

The percentage increase means add a given percentage of a value onto the original value.

if the circulation is X
at end of year 1 it is 2X
at end of year 2 it is 6X
at end of year 3 it is 4.5X

from year 1 to year 3 the circulation goes from 2X (original value) to 4.5X

So let’s write 4.5X = 2X + 2.5X

2X is 100% of original value
2.5X is 125% of original value

so percentage increase from 2X to 4.5X is 100 + 125 = 225

(2X x 225/100 = 4.5X)

using real numbers, let’s say your original value is 60 and you want to increase it by 20%, then:
100% = 60
20% = 12
So 60 + 12 = 72

however the percentage increase is 100 + 20 = 120

(60 x 120 / 100 =72)

I had to read over a few times but you're correct

100% of 200 is 200

200% of 200 is 400

225% of 200 is 450

If I then INCREASE 200 by 225%, I need to take 200 and add on 450, so I get 650.

It’s the same as a typical Daily Mail headline

”MUMSNETTING CAUSES 50% INCREASED RISK OF SCURVY”

When actually the increased risk has gone from 0.0001% to 0.0002% ie an infinitesimal increase in risk but still an increase in risk percentage of 50% mathematically

What? 😂

This thread is a real eye-opener. It's not even people who have no interest in maths or those who think they're bad at maths who are commenting and fundamentally misunderstanding the question, it's people who genuinely, confidently believe they're quite good at it. Astonishing.

This is where you are wrong. You say

“This is wrong. You need to calculate the percentage increase between X and 2.25X.
If you increase X by 100% you get 2X. By 125% you get 2.25X.”

The question doesn’t ask you to calculate the percentage increase it asks you what was the percentage increase. End Y3 is 2.25 times end Y1 so the percentage increase is, I’m afraid, 225% - as per @Horsie’s explanation.

What you have done is look at the difference between end y1 and end y3 and expressed that as a percentage of end y3 (I think, from memory). That is not what the question asks. There was no sanctimony in my post; you are obviously interested in this but are also wrong, and don’t seem to have the skill set to understand why. In those circumstances further education on this matter might be something you would enjoy?

I sadly don’t have a maths degree, but fully intend to get one when I retire, so more than happy to go back to school when I have the resources to do so. But what they won’t be teaching me is that the correct answer to that question is anything other than 225%.

It’s 100 + 25. 125%.

You have too many years. They actually say ‘the third year’ (for which you have year 4).

Can’t believe it’s 1.30am and I’m still entertained by this thread 😂. Hoping you get this job OP, it shall give me more confidence in how policy is implemented lol

I love how you’ve confidently said this without tacking your mathematical colours to your mast 🤣

The end of y3 sales are 225% of the end of year 1 sales BUT that is not the question. To get the increase you have to take the original 100% off. The Op is correct.

Argh I got my numbers wrong 🤣🤣

But if you know, you know

I don't even know where to start with this comment.

The question doesn’t ask you to calculate the percentage increase it asks you what was the percentage increase. **

now I’m completely lost 😂😂😂

End Y3 is 2.25 times end Y1 so the percentage increase is, I’m afraid, 225%

Something which has increased 2.25 times has increased by 125%.

They presumably think there has been massive deflation.

😂

No. You don’t just divide one number by the other to work out the % increase.

If you double something, you are increasing it by 100%. If you earn £20 an hour and get a 100% rise, you will earn £40 an hour. If you normally get 20 chips with your fish but today you get 40 chips, that is a 100% increase.

If a price rises from £40 to £80, that is a 100% increase/rise. If it rises from £40 to £90, that is a 125% increase/rise.

@Samscaff

One hundred percent of 200 is 200.
Twice 200 is 400. That's not the same as 100 percent of 200.

It's an increase by virtue of the fact that we are adding over 100 percent of a quantity.

If you had 100 grapes, a portion of those grapes could only ever be less than 100 grapes, right?

The 25% is the increase.

200 x 1 = 200
25% of 200 is 50.
200 + 50 = 250. So a 25% increase of 200 is 250.

But we are not looking for an answer of 250.
We need an answer of 450.
We are looking for a percentage increase of 200 that fits 450. (200 + 225% is 450.)
The reason we're looking for 450 is because we needed to assign a numerical value (not a percentage) to the starting circulation. OP chose the starting number of papers sold to be 100 papers. It doesn't matter what starting number we use, because what matters is the percentage increases of whatever number we decide to start with.

Start of Year 1, the circulation is 100 papers
End of Year 1, the circulation is 200 papers, because it doubled from 100.
End of Year 2, the circulation is 600 papers, because it trebled from 200.
End of Year 3, the circulation fell by a quarter. That is, a quarter of 600.
600 minus one quarter is 450. (A quarter of 600 is 150. So 600 - 150 = 450.

The question asks by what percentage did the circulation increase from the end of Year One to the end of Year Three.

By assigning a numerical value to the starting circulation, 100 papers, we know that by the end of Year One the circulation is 200 papers and by the end of Year Three it's 450 papers.

When 200 papers increases to 450 papers, that's a 225% increase.

You can't read?