Maths test - to think Civil Service have it wrong?

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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?

You do not start with 100%. What came before the end of Year One is irrelevant to the question.

By that logic, at the end of year 3 it hasn't turned fallen by a quarter. So it would be 500%.

Actually ignore that, you are right. It’s asking for %increase.

Maths doesn’t have a view. It has a correct answer. If circulation doubles in a year, then by the last day of that year it has doubled.

Exactly

So it's starts at 100% because it's 100% of the number sold at that point

If it was from the start of year 1 you'd start with 100% x 2 = 200% x 3 = 600% - (600÷4) = 450%

You're making 100 a number not looking at it as %

You are completely right OP. There are some mad answers on here.

Whatever happened before the end of Year One is irrevant. It’s asking for the increase between the end of one and three.

I think you're correct OP

You start with 0. It doesn’t matter what numbers you assign, the percentage between the end of one and three remains the same.

What a pathetic dig.

No, because a year after (for example) 01/01/25 is 01/01/26…ergo it’s doubled in a year, which is the first day of year 2.

No. It’s asking for the percentage increase between the end of year one and the end of year three. You can completely ignore anything which happened before the end of year one.

You can choose any number. I just used it to illustrate the maths. The percentage increase using numbers or not using numbers remains 125%.

As i see it, the end of year one is 100%. Doesn't matter that it doubled in the previous year. You then treble it and take a quarter off that leaving 225%.

You could stick any number in

So 20 sold pre Y1, doubles to 40 at end of Y1
40 trebles to 120 at the end of Y2
120 falls by 1/4 to 90 at end of Y3
The % difference between 20 and 90 is not 125%, it's just over 400%

Which is why you don't add in numbers but work out with the %

If year 2 end is x3 cf end year 1 you have a 300% increase. At year 3 end you’ve lost 1/4 (75%), so the change from end year 1-3 is 225%.
You need to ignore the first year entirely for the correct answer.

OP is right, the test is wrong. The answer is 125%. If circulation begins at 100 units, by the end of year one/start of year two circulation is 200 units. At the end of year two it’s 600 units, and at the end of year three it’s 450 units. (450/200)-1 = 125% increase.

For those who are saying 225% - yes it’s 225% of 200, but that’s a 125% increase on 200.

I agree with you OP.
100% (£200) + 125% increase (£250) = £450

One of the things I love about maths is that the correct answer is the correct answer and not influenced by opinion. It has riled me that it can’t be answered correctly.

is it definitely asking for the % increase or could it be asking what the end result is as a % of the starting figure? Are you able to share the exact wording of the question?

Yes so from 100% of the circulation because at the end of Year One the circulation is 100%

Not the number 100

The %

Circulation at the end of year 3 is 225% of circulation at the end of year 1.

The increase in circulation is 125% though. You are making the same mistake the person who set the question and I made.

Nope. A 3x increase in something (ie ending number is three times larger than starting number) is a 200% increase on the starting number, not a 300% increase. 600 newspapers sold is a 200% increase on 200 papers sold.

The formula is (x/y)-1, not just x/y

Oh and Maths doesn't always have an Exact answer....