GCSE Edexcel Maths Unit 3 19/06/2012 Exam Discussion

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It's easy once you grasp the entire way on how to do it, here's how ^2 = Squared:
Lets call the small circle A and the bigger circle B
Area of circle A =
0.5*pi(x+3)^2 (Area of circle = pi * r^2)
expand it out gives us
0.5*pi(x^2+6x+9)
Area of circle B =
pi*(2x)^2
Expand it out = pi*4x^2
4pi*x^2-0.5*pi(x^2+6x+9)
divide the whole thing by pi so it now =
4x^2-0.5*pi(x^2+6x+9) which if divide by 0.5 it goes into the equation so
1/2*pi(8x^2-(x^2+6x-9) now simplify it becomes
1/2*pi(7x^2-6x-9)=84pi
now divide by 1/2pi so you get
(7x^2-6x-9)=168
now make it so 0 is on one side so -168 which =
7x^2-6x-177=0
now just use completing the square or the quadratic formula, whichever you prefer and you've got your answer so, the answer is 5.475291923615913 however it doesn't state it to 1 decimal place so this is still the right answer.
Sorry if it's a little complicated didn't know an other way to explain it. :s-smilie:

Also I've pretty much revised everything but the only thing I still can't fully grasp is how I'm going to remember the equations to the volume of 3d shapes :frown:

the only thing I can do is pray it doesn't come up :biggrin:

Hey, I don't quite understand how you answered this question, could you perhaps describe each stage and describe what you are doing and how you are doing it please :smile:

It would be very helpful and why did you times 0.5 at the start. Thank you very much :smile:

Reply 181

Herschel

what mark would be a B - 118 ums

Reply 182

lorobolorolo

Original post by ThirdSnowLeopard

Could anyone help me with this?
Meant to be a fraction, but since I can't type it like that...
Solve: (3x-2)/(1-2x) = (x+6)/(x-8)

I know the answers, but I don't know how to solve it. I've tried a few times with sums of the same type and keep making mistakes along the way. :s-smilie:

Also, does anyone know how to do this?
Use the compound interest formula to find interest rate p.a if £8000 has a future value of £10724.

Ok here is what I would do:
(3x-2)/(1-2x) = (x+6)/(x-8)

1. Because there is an equal sign in the middle I would try and get all the x on one side and the numbers on the other side. So I would take the denominator (1-2x) to the other side and (x-8) to the opposite side. When you take something to the other side u have to do the opposite. So the opposite of divide is multiply so u have to multiply like this.

(3x-2)(x-8)=(x+6)(1-2x)

2. So next u have to multiply out the brackets because in between the two brackets there is supposed to be a multiplication sign. So it would be:
By the way x^2 is supposed to mean x to the power 2.

3x^2-24x-2x+16=x-2x^2+6-12

3. Basically I got that from multiplying 3x with x and -2 with x and so on...
Next you have to simplify by collecting all the like terms. So it would be:

3x^2 - 26x+16= -2x^2 - 11x+6

4. Now u have to bring everything to one side so that it is equal to zero. When u take something to the other side u have to do the opposite operation. For example when you take -11x to the other side it becomes +11x. So it would be:

5x^2 - 15x+10=0

5. Now u can divide it through by 5 because 5, 15 and 10 are all divisible by 5. So it would be:

x^2 - 3x+2=0

6. The last step is to factorise into 2 brackets to find the values of x. So it would be:
(x-1)(x-2)=0

So the answers are x=2 and x=1

I hope u understood becoz its quite difficult to explain on the computer. It would have been much easier to explain face to face.

Now for this question:
Use the compound interest formula to find interest rate p.a if £8000 has a future value of £10724.

the compund interest formula is

F=S(1+ i)^n

F is the final amount. S is the starting amount. i is the interest rate and n is the number of years.

So u put in the numbers which u know into the formula.
F=10724
S=8000

10724= 8000(1+i)^n

I'm guessing that the number of years is 1 as it didn't mention it in the question. So what I would do is rearrange the formula to get i as the subject. So I would divide 10724 by 8000 becoz I'm taking 8000 to the other side. So it would be:

10724/8000= (1+i)
1.3405=1+i

So i is
1.3405-1=i
i=0.34
To get the percentage you have to multiply by 100

so I guess interest rate is 34%

this last question was quite hard so I'm not too sure if it is right.

Reply 183

Dilzo999

Original post by Hi, How are you ?

Hey, I don't quite understand how you answered this question, could you perhaps describe each stage and describe what you are doing and how you are doing it please :smile:

It would be very helpful and why did you times 0.5 at the start. Thank you very much :smile:

I divided by 0.5 as it only gave us the diameter and not the radius and radium = half the diameter.

Reply 184

EllieGibson

might sound a bit dumb but has anybody got just a topic list they can put up for me please? i'm struggling with this revision xxx

Reply 185

Skittle123

Sorry if this has already been asked, but does anyone have a clue as to what might come up in the exam??? :smile:

Reply 186

A193

Original post by Kayannk

I know right! I'm not saying the last two units were easy... but compared to this one!

Good luck friend!

Thanks,you too. how many ums do you have at the moment?????????

Reply 187

kashagupta

Original post by EllieGibson

might sound a bit dumb but has anybody got just a topic list they can put up for me please? i'm struggling with this revision xxx

It doesn't sound dumb at all! Here you go :smile:

Is this what you're referring to?

Reply 188

EllieGibson

thankyou so much! may have just saved my maths gcse!!! need to get 140ums to get an a!!! no chance!

Reply 189

dreams150

Hey guys I've been looking everywhere over the the web and found a really good site with all the previous past Unit 3 edexcel past papers.

http://mathsbedwas.wikispaces.com/Unit+3+-+Higher

Most of the papers have mark schemes, for the few mark schemes that aren't there you can easily use google to find it by typing the paper code, the year and edexcel GCSE maths and should come up.

My only problem is that I cant find the grade boundaries. I can only find the converted UMS mark not the raw grade for the paper. If anyone can point me to the right direction and show me 2011 and 2010 grade boundaries for the paper 5384H/13H unit 3 edexcel papers which are out of 60 I'd be highly appreciative.

Thankyou :biggrin:

Reply 190

PompeyFTW

Try Googling it: 'Edexcel June 2010 grade boundaries' or whatever, and it should come up with a PDF file - scroll down to find the units you are doing.

Reply 191

zeezee180

I need to get 136 out of 180... grr does anyone know what raw mark that would be?

Reply 192

zeezee180

btw can someone please explain Sin, Cos and Tan to me? I am so baffled.

Reply 193

kashagupta

Original post by zeezee180

I need to get 136 out of 180... grr does anyone know what raw mark that would be?

about 68/80 :smile:

Reply 194

vamos talal

Original post by MathsMind

Hi,

Here are some mock and practise papers for Unit 3 and the Mark Schemes. Credit goes to Edexcel for producing great quality papers for us. Enjoy and please comment

Happy Revising!!

Can you please tell me whether or not you've got answers for the churchill paper??Thank you very much!

Reply 195

ILOVEWHALES

Help! The mark scheme for 2010 EHA Unit 3, is for a diffrent paper! Please can you put the correct mark scheme up as soon as you can if possible! :confused:

Reply 196

Adamtemps1

Original post by kashagupta

about 68/80 :smile:

What do you think 140/160 will be in raw marks?

Reply 197

kashagupta

Original post by Adamtemps1

What do you think 140/160 will be in raw marks?

It's approximately half really! So it would be 70/80 :smile:

Reply 198

Adamtemps1

Original post by kashagupta

It's approximately half really! So it would be 70/80 :smile:

Thanks

I need that for an A* but I'm scared I won't get it because I make so many silly mistakes :frown:

Could it be lowered though because grade boundaries tend to vary a little and because we are the first to take this exam it's bound to have low grade boundaries as everyone found it hard ?

Reply 199

kashagupta

Original post by Adamtemps1

Thanks

I need that for an A* but I'm scared I won't get it because I make so many silly mistakes :frown:

Could it be lowered though because grade boundaries tend to vary a little and because we are the first to take this exam it's bound to have low grade boundaries as everyone found it hard ?

Yeah I'm in kind of the same situation! And don't worry, it's quite a long paper and you'll have loads of time to check over! And 70's only an approximation, it could be much lower :smile: