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?

I really hope someone (/power of Mumsnet) has brought this to the attention of whoever is in charge of these tests at the CS …..and that @Sharingaroomtinightthen gets offered a job, maybe she should be checking over their admissions tests as a start!!

Your husband is wrong. Assume circulation at the start of year one is 100 copies. By the end of year 1 it’s 200 copies. By the end of year 2 it’s trebled to 600 copies, then in year 3 the figure as a whole decreases by 25% to 450. It’s the % difference you’re after from the end of year 1 to the end of year 3. So you subtract the end of year 1 figure of 200 from the end of year 3 figure of 450. That gives you 250. Divide that by 200, which was the circulation figure at the end of year one = 1.25. Multiply by 100 to get the % difference = 125%.

To calculate a % increase, we need to compare the end number with the starting number.

Fir ease you can call your starting number (end of Y1) 100. (It makes no difference what happened before that.)

You then triple it for end Y2 (300) and then reduce that by a quarter for end Y3 (225).

The figure has gone from 100 at end Y1 to 225 at end Y3. That is an increase of 125.

If the figure had doubled, that would have been an increase of 100%. It did better than that - it went up by one-and-a-quarter times the starting figure of 100. 125 as a % of 100 is 125%.

Some "maths expert". I've got a maths degree and was a maths teacher so I've seen plenty of ambiguously written questions, or questions where you have to make an assumption to proceed, but I can't see any ambiguity in this one. Where is there ambiguity?

I honestly think some of the posters on here think that if there's a 70% sale on and then there's another 30% reduction added then they'll get stuff for free!

Or they understand that, but then somehow think that a 100% increase is the same as a 0% increase.

I wonder which the civil service question setter falls under.

I know he is wrong! I meant I agreed with both my uni kids.

I am clearly rubbish with wording myself. I didn’t even say I had two kids. What a fool! Maybe I should join the civil service ;-)

Incorrect. Read the thread - even the last few replies should help.

There isn’t, but somewhere along the line the question setter has missed a step because the answer is 125%.

It seems obvious to me that the OP is right.

Am decidedly unimpressed by the civil service question setters.

Ah, sorry, misunderstood. Apologies.

I understand this logic based on the wording of the question however I see the wording as the percentage increase in circulation from the base in relation to end of year 1 to 2 not using the base as the number at end of year 1 only the difference from end of year 1 and end of year 2.

Try it like this: you use the number at the end of year one and the number at the end of year two. Don't use anything else you are not being asked to include.

To take it to a logical yet ludicrous example, if you followed a recipe from a recipe book, you would only include what was stated. For example, 100g of flour, and 25g of sugar. At no point would it be reasonable or ideal to decide you should be adding a quantity of weedkiller to the recipe, just because you felt drawn to bringing something else in of your own choice.

You have 5 possible answers and then you have the correct answer which isn’t an option.

I think either the test is wrong. Whoever designed the question forgot to take off the 100% that they began with to find the percentage increase. (So did I initially, in my defense is it was very very late and I was very very tired)
or
They are not actually looking for the correct answer, they are looking to see who has the ability to follow their thinking patterns with the limited options they have in front of them.

Little to nothing you are saying makes sense.

What two numbers are you trying to compare? What is the starting number you are using (100, I think?) and the final number?

To help, if you are starting from a baseline of 100 newspapers per year:

200 newspapers at the end of year 3 is a 100% increase
300 papers is a 200% increase
400 papers is a 300% increase
500 papers is a 400% increase
600 papers is a 500% increase
700 papers is a 600% increase

I agree op

Others have weighed in on this post since, and I have only skimmed those comments. However, the PP I was replying to appeared to have understood ‘percentage increase’, and requested the term for 'percentage change over the base number’. They qualified this by saying "It could be 100% change is no change.” This suggests they are looking for the whole as a proportion of the original (ie the unit after increase as a proportion of the original unit). The term for that is indeed ‘percentage’.

They were wrong of course. 0% change is no change. 100% is 100%. 100% change is 200% (or zero).

OP I disagree with your answer in a totally we're all good way. But seriously it would be really interesting for you to tell them they're wrong, if you don't get the job, to see what they actually say. Imagine the fun you could have this?! And the fun we could all have when you post about it?!

I'd love to know what qualifies them as an expert 😂

No, it was my poor wording!

Everyone please humour me IF we take the wording OUT and use 100 as the base to gauge the percentage increase what would your answers be?

Base 100

End of Year 1 200

End of Year 2 600-150 = 450

What percentage increase from base 100 to end of year 2?

What percentage increase using the base 100 from end of year 1 to end of year 2? IE the difference from end of year 1 to end of year 2 but using the base as 100 not 200.

I know but given the choice of answers what makes sense to me is 450%

End of year two is not 450. It is 600.

End of year one is 200.

End of year two is 600.

End of year three is 450.

Difference between 200 and 450 is 125%.

The question is fine and a pretty standard one. You maths friend is wrong probably misread the question, the options for the answers are wrong.

I did it the same way and got the correct answer - 125%. Starting number 100, 100% increase to 200 at end of year one, trebled to 600 at end of year 2, decreased by 25% to 450 at end of year 3. Subtract 200 from end of year one from 450 end of year 3 = 250. Divide by the circulation at the end of year one: 250 / 200 = 1.25, then multiply by 100 to get the percentage = 125%

From the end of year 1 to the end of year 2 is a 200% increase.

I never said end of year 2 was 450% the number of copies was 450.

I get end of year 2 is 350 difference between base 100 (450-100) which I calculate as 650 %.

250 is difference between end of year 1 and 2 (450-200) and from base 100 I get this as a 450% increase which is the only answer on the drop down you can choose.

Hence why I would choose 450% as the answer.