Active discussions

Meet the Other Phone. Child-safe in minutes.

Meet the Other Phone.
Child-safe in minutes.

Buy now

Please or to access all these features

Talk
AIBU?

Share your dilemmas and get honest opinions from other Mumsnetters.

Original poster

To ask for your help with a fractions question??

30 replies

raspberryriot · 10/02/2015 14:23

I hope you don't think AIBU to ask for help with this maths homework question? Just posting here for traffic. My DD (Year 6) has been set some really difficult maths homework and I promised I'd help her with the workings out but not just give her the answer. I was terrible at Maths at school but just managed to scrape my O' Level. Anyway the question is:

Write the missing number as represented by x.

160
= 0.2

x

I have found out via the internet that the answer is 800 (it's a Level 6 SATs question) but I don't know how to work it out? Am I just plain stupid?

I will be writing a note to the teacher to explain that DD found this too difficult but I'm curious to know how you do it so I can help her?

I reckon it's something to do with Cross Multiplication and Algebraic Fraction Equations but my brain has glazed over....

Clear workings out would be much appreciated!!!

Thanks in advance.

OP posts:
Original poster
raspberryriot · 10/02/2015 14:24

EEEk the fraction didn't show up properly on my post...

It is 160 over X = 0.2

Thanks!

OP posts:
Seeline · 10/02/2015 14:25

I'm not sure that the typing of your question has come out particularly clearly?
Could you try a different layout.

NeedABumChange · 10/02/2015 14:26

It's 800.

HamstersDontHaveFeet · 10/02/2015 14:26

Decimals not fractions?

0.2 =160

0.2 x 5 =1

Therefore 160 x 5 = 800

NeedABumChange · 10/02/2015 14:27

1 divided 0.2= 5
5x160=800

Seeline · 10/02/2015 14:27

Ahh - that's better!
Basically you are dividing 160 by something to get 0.2. Therefore if you divide 160 by 0.2 you will get the answer X ie 800.

It's basic division/multiplication. Smile

LurkingHusband · 10/02/2015 14:28

160/x = 0.2

160/x x = 0.2 x

160 = 0.2 * x

160 / 0.2 = x

800 = x

HamstersDontHaveFeet · 10/02/2015 14:28

160/x =0.2

Times both sites by x
160 = 0.2x

Therefore times both sides by five to get x
160 x5 = 800

KatyMac · 10/02/2015 14:28

That's odd - I got 32 Blush

160/x=0.2
so
160=0.2x
so
160*0.2=x
so
32=x

No idea why the answer is 800.......i must be doing it wrong

NeedABumChange · 10/02/2015 14:28

I don't think you should write a note. It's pretty simple and should be done easily by a child expected to pass their maths level6.

MumSnotBU · 10/02/2015 14:28

How many 0.2s in 160?

Or how many fifths in 160? There are 5 fifths in 1

So 5x160=800

HamstersDontHaveFeet · 10/02/2015 14:28

Xposted with loads!

ImperialBlether · 10/02/2015 14:29

Well the way I would look at it is that 160 is 1/5th (or 0.20 or 20%) of the total. You then have to find out what the total is.

4/5ths would then be 4 x 160 which = 640.

The remaining 1/5th you know is 160, so the total is 800.

So the sum would be 160 over 800 equals 0.2.

KatyMac · 10/02/2015 14:29

Ignore me - I'm a dork & half asleep

HamstersDontHaveFeet · 10/02/2015 14:29

Katy Mac, you multiplied instead of dividing.

penny13610 · 10/02/2015 14:30

assume the question is 160 over 0.2 = X
you are not allowed decimals in fractions so multiply top and bottom by 10
you then have 1600 over 2
much better but we would like a one on the bottom
so divide top and bottom by two
800 over 1
or plain old 800
if feeling bold you could just start off by multiplying top and bottom by five

MumSnotBU · 10/02/2015 14:31

1/5 of 800 mumsnetters are too tired to do fractions

160 to be precise Grin

PervyMuskrat · 10/02/2015 14:31

Another way to think about it once you get to the stage of 160 = 0.2x is to multiply both sides by 10 to hey a whole number rather than a fraction so you get 1600 = 2x and then divide by 2 to get 800 = x

Nolim · 10/02/2015 14:32

160/x=0.2
160/x=1/5
Muliply by the product of the demonimators 5x
5x(160/x)=5x(1/5)
5160 =x
800=x

Ta-da!

PervyMuskrat · 10/02/2015 14:32

X post with penny Smile

Original poster
raspberryriot · 10/02/2015 14:32

Oh thank you so much all you lovely people. I think I was trying to overcomplicate it. I have a tendency to do that! I was so terrified of Maths when I was younger that I really want to try and keep up with what my 4DC are doing! I'll be able to help her now.

OP posts:
PatriciaHolm · 10/02/2015 14:33

KatyMac - you need 160/0.2 = x as your third step, not 160*0.2 =x.

You could also look at its as 160/x = 0.2 means 160/x = one fifth, so 160 is one fifth of x, and do 160x5. I'm surprised its Level 6 to be honest, it's not that hard.

Ilovehamabeads · 10/02/2015 14:35

What's wrong with writing a note need ? It's just to highlight to her teacher that she found it difficult and perhaps needs a recap on the methods. Not all children understand something first time round.

negrilbaby · 10/02/2015 14:35

160 divided BY x is 0.2.

If you think about simple numbers and how they connect:

If 16 divided by 8 is 2 we also know that 16 divided by 2 is 8
so in this case
160 divided by x is 0.2 then 160 divided by 0.2 is x.

160 divided by 0.2 means work out how many 0.2 there are in 160.
There are 5 lots of 0.2 in 1 (0.2 x 5 = 1) and so
160 x 5=800 lots of 0.2 in 160.

NeedABumChange · 10/02/2015 14:45

ilove
I think I was picturing a note complaining that the homework was too hard. But imagine being a teacher that gets a note every time a child has difficulty on a single question on a piece of homework!

I would agree with talking to the teaching if the Dd was hugely struggling with the entire piece of homework though. You're probably just a bit out of practise raspberry it's lovely that you are helping her.