Maths help please.

[RockYourSocksOff]

I asking these questions.

Ok, so dc are doing median, mean, mode and range. Ds hasn’t seen this question yet so I’ve no idea if he will get it straight away or require my ‘help’ He’s stayed out overnight so will be doing this on his return. If he needs my input I’ll then be able to breeze in and act as if I know what I’m talking about

Here goes.

A student had taken six tests and received scores of 17,19,16,19,15,20,14. The eighth test was coming up and the student wants to know:

What was needed on the eighth test to have a mean score of 17. Find the seventh test score.

Thanks in advance.

If the mean is 17 then the whole lot adds up to 17 x 8.

So do that sum and then take away all the others and what is remaining is your test score that will give your mean of 17.

Is there a typo? It says they've taken 6 tests but there are 7 scores written down.

No xyz, that’s what has been confusing me.

One way is to set is up as a algebra equation with the missing score value as a

Another way to work it out is to work out how many values lie above the mean and by how much and below the mean and by how much and then wprk out what value makes this equal

Sorry i missed there was two values missing. You need the second method not the first

Thanks Sackrifice.

I’m not sure I still get it totally.

Got to pop out. Will be back later to check.

That's a really poorly worded question...

So he's taken six tests but they've presented seven results then asked what was needed on the eigth test to get that mean, but then asked for the seventh result!!

Eh?!

So
17-17=0
17-19=-2
17-16=1
17-19=-2
17-15=2
17-20=-3
17-14=3

So 6 lower
7 higher

So 15 and 18 would be one option 14 and 19

Thats assuming my sums are right. They may not be cos im ill and on a phone but thats the method

The idea is to get your deep understanding of what the mean is and what it does. Its a really clever question.

But unless theyve thrown in a bit if information about the median or mode (or my sums are wrong) there not one definite answer just pairs of answers

A very badly worded question. You have been given 7 results so I would assume and write this in the answer they actually mean
'a student had taken 7 tests and received scores of .....'
what score do they need in the 8th test to have a mean of 17.

Assuming that 17 x 8 = 136
To find the 8th result minus all 7 results you have from this (136) is 16

Despite getting an A at GCSE maths I'm too old for A-Star I only learned this a couple of years ago, when retraining.

Hey diddle diddle
The median's the middle
You add and divide for the mean
The mode is the one that appears the most
And the range is the difference between

I suspected the person rewriting it has added on a 7th test and not reworded the question.

I’m not confident enough in maths to have questioned the wording, I just thought I couldn’t see what the answer should be.

It’s a sheet which has been printed from an online resource.

Thanks for your replies. Makes a bit more sense now (I think).

The idea is to get your deep understanding of what the mean is and what it does. Its a really clever question.

Um... haven't you confused median and mean in your answer?

Mean is average isn't it? I agree with sackrifice's post.

Although the "7th test" thing doesn't make sense given there are 7 scores.

Nope. The median value would be if you lined them all found the value thats in the middle
So
17,19,16,19,15,20,14 would become
14 15 16 17 19 19 20
The median value is the one in position 4 (7+1)÷2 so if you were 2 values short you'd need anything larger than 17 abd anything smaller than 17 so 13 and 20. If you were one value short you would need seventeen....

Id better stop because else i'll start working out the quartiles and interquartile range.

What i cant do is count and realise there was 7 values (9 in total) there not six (8 in total). So sackrifice is right the question is wrong. But my method works

sackrifices method works too. only if there were two missing values they jointly would need to add up to the result

The question is nonsense. You can’t say a student has taken 6 tests then give 7 test scores and then ask for the 7th test score.

Giving seven test scores and asking what the eighth would have to be to have a mean of 17 is a really common maths question, so I’d answer that one.

only if there were two missing values they jointly would need to add up to the result of 9×17

I can't type today.

No wonder I was confused. I’ve typed it out just as it appears on the paper. Glad I got to it before Ds.

Can you take a photo of it?

Sheet is back at school now but I found the same one online.

Well there you go. The teacher sensibly used external resources to save re-inventing the wheel, but didn't realise this wheel had a spoke missing.