Maths experts in here!

[old.UKTwister]

Ok i have my maths gcse in about a week and theres some questions that i really have no idea to do so i'm hoping you can all help me

1) A box measures 24cm by 18cm by 15cm. The box is to be filled with cubes of equal size.

What is the length of the side of the largest cube that could be used to fill the box?

2) Mandy is x years old. Her brother is 5 years older than mandy. The product of their ages is 84.

Show that X^2 + 5x - 84 = 0

3) Simplify fully the expression

8x^2 + 24x
___________

2x^2 +5x - 3


4) You are given that (x+a)^2 + b = x^2 - 6x +13

Find the values of a and b


5) You are given the formula: y = 5 + x over x




Rearrange the formula to give x in terms of y

6) Simplify (3xy^2)^4

Note: ^ means to the power of to people who didnt know.

I'd be happy if any of you could help with some of these, cheers

 

[(Shovel)]

I've not got the time to do them all for you - got a Databases exam tomorrow a Matrix film to go see (yes yes, priorities),.

Q1 is simply finding the common factor. Erm, and unless I've totally lost it this evening, the answer is 3 - since that is the largest number that will go whole into 24, 18 and 15.

 

[Durzel]

Do some revision you lazy fuck.

Otherwise, just fail it. Ultimately someone has to end up working in McDonalds, to preserve the natural order of the cosmos!

 

[GDW]

Thats a bit harsh. Maybe hes worked his socks off and is stuck on a few topics. Nothing wrong with asking for help

 

[old.UKTwister]

I have actually revised a lot, the revision guide doesn't cover these type of questions very well.

 

[mr.Blacky]

Originally posted by old.UKTwister
1) A box measures 24cm by 18cm by 15cm. The box is to be filled with cubes of equal size.

15

What is the length of the side of the largest cube that could be used to fill the box?

2) Mandy is x years old. Her brother is 5 years older than mandy. The product of their ages is 84.

Show that X^2 + 5x - 84 = 0

brother = X + 5, Mindy = X -> (X+5) * X =84 -> X^2 + 5X = 84 -> X^2 +5X-84


3) Simplify fully the expression

8x^2 + 24x
___________

2x^2 +5x - 3

16x+24=0
4x +5 = 0


etc.

/edit unless my math sucks...

 

[nath]

Re: Re: Maths experts in here!

Originally posted by mr.Blacky

Originally posted by old.UKTwister
1) A box measures 24cm by 18cm by 15cm. The box is to be filled with cubes of equal size.

15

Wrong, it's 3. you'd get a 15x15x15 cube in there, but there'd be wasted space. It's a poorly asked question tbh, but what it IS asking is what's the biggest cube size that would completely fill out the box. So shovel is right, it's the common factor thing.. which is 3. So each cube would be 3^3.

 

[old.Reverend Flatus]

Been ages since I did maths but I'll have a go -

1. This would be the highest common factor - since 24 = 3 x 2 x 2 x 2, 18 = 3 x 3 x 2 and 15 = 5 x 3, hte highest common factor is 3.

2. Expressing the question algebraically - x(x + 5) = 84
multiplying the left hand side out gives x^2 + 5x = 84
subtracting 84 from each side gives x^2 + 5x - 84 = 0

3. To simplify 8x^2 + 24x divided by 2x^2 + 5x -3
factor out the top and bottom terms to give 8x(x + 3) divided by (2x - 1)(x + 3)
divide top and bottom by (x + 3) to give 8x divided by 2x - 1

4. Surely there's not enough information for this one. There are three unknown values but only one equation given, you need three to solve by simultaneous equations.

5. To simplify y = 5 + x over x
multiply each side by x to give xy = 5 + x
subtract x from each side to give xy - x = 5
factor out the left hand side to give x(y - 1) = 5
divide each side by y - 1 to give x = 5 over y - 1

6. Just multiply the powers by 4 to give 81x^4y^8

 

[Panda On Smack]

Far from helpful but the age old saying of 'when the fuck am i gonna use these fucking sums in my life?' springs to mind.

Obviously there are variants of the above but thats roughly it

 

[Munkey-]

if those are the questions coming up then I'm fucked.

I'll rely upon the past papers our teacher has given us methinks and work from that.

 

[old.UKTwister]

nice 1 rev

if those are the questions coming up then I'm fucked.

Depends what paper your doin, if it's higher then yes. If it's intermediate or foundation then the questions are usually in the form of 2+2 = ??

 

[.Cask]

Can't remember my higher maths paper being that hard. Took me fuckin ages to do all of those sums and there's still 1 that I'm not sure about.

Anyway good luck. GCSE's don't really matter a whole lot so don't worry about it too much.

 

[FatBusinessman]

Originally posted by old.Reverend Flatus
4. Surely there's not enough information for this one. There are three unknown values but only one equation given, you need three to solve by simultaneous equations.

As you're asked to find a and b, you can assume that it's true for all values of x and equate the coefficients.

So you multiply the equations out:

(x+a)² + b = x² - 6x +13

x² + 2ax + 4 + b = x² -6x + 13

(2a)x + (4+b) = (-6)x + (13)

Thus 2a = -6, so a = -3

And 4+b = 13, so b = 9

 

[FatBusinessman]

P.S. I've got 5 Cambridge exams coming up in a week or so - wanna swap?

 

[Embattle]

This reminds me why I ended up fooking hating maths and ended up getting in to a big arguement with a teacher once, utterly pointless equations.

 

[.Cask]

Originally posted by FatBusinessman


(x+a)² + b = x² - 6x +13

x² + 2ax + 4 + b = x² -6x + 13

Call me a dumbass... but where did that 4 come from?

 

[Embattle]

dumbass

 

[Kempo]

uni maths paper in half an hour, joy :/

 

[old.Fweddy]

I'm good at maths but there was no chance I'd ever keep it up with all the stupid pointless sums you have to do.

 

[Gef]

Originally posted by Munkey-
I'll rely upon the past papers our teacher has given us methinks and work from that.

I heard on the news some teacher was selling current papers for like £20 a piece or something! Nice

 

[old.Reverend Flatus]

Originally posted by .Cask
Call me a dumbass... but where did that 4 come from?

Yes, where did it come from?

 

[nylex23]

It should be a^2 instead, so b = 4 (as a^2 + b = 13 with a = -3).