Gcse maths help!

Bigfooty

Hi does anyone know how to do inequalities? I am really really stuck I have looked at my notes but they don't make any sense - please help thanks :cool:

Can be solved in the same way as normal equations (either balancing method - d sma eto each side, or moving things across) just leave the inequality sign in there but pretend it is equals.

Also with more complex ones you can split them.

And then re-join them at the end.

See: http://www.bbc.co.uk/schools/gcsebitesize/maths/algebraih/equationsandinequalitiesrev3.shtml?1c2a#solution1 for full details.

Hope that is what you were after.

Reply 4

This isn't about inequalities.but on gcse papers theres always an annoying question such as:

Mr Smith invests £2000 in a savings account at the beginning of the year.
The money earns 3% per annum compound interest.
The interest is added on at the end of each year.
How much money will Mr Smith have in his account at the end of the year?

It's really annoying because you have to work it all out separately, the interest and then use that answer to work out the next years interest - is there a quicker way? it is only worth 3 marks.

If you type out some inequalities i may be able to help you :rolleyes:

Reply 5

Spy_Lord

7

This isn't about inequalities.but on gcse papers theres always an annoying question such as:

Mr Smith invests £2000 in a savings account at the beginning of the year.
The money earns 3% per annum compound interest.
The interest is added on at the end of each year.
How much money will Mr Smith have in his account at the end of the year?

It's really annoying because you have to work it all out separately, the interest and then use that answer to work out the next years interest - is there a quicker way? it is only worth 3 marks.

Don't waste time in the exam working them out individually. Use the compound interest formula:

Total=

There a some really slight variations on that but memorise it and you'll be fine.

PS: anyone know how to include the pic directly in a post?

Reply 6

m:)ckel

14

Spy_Lord

PS: anyone know how to include the pic directly in a post?

Click 'Manage Attachments' button in the 'Additional Options' section when posting a message.

Reply 7

Spy_Lord

Don't waste time in the exam working them out individually. Use the compound interest formula:

Total=

There a some really slight variations on that but memorise it and you'll be fine.

PS: anyone know how to include the pic directly in a post?

Oh thanks, our teacher never taught us that - you couldn't elaborate on the formula though oculd you please, it looks confusing what to do.

Reply 8

gemma.....

Oh thanks, our teacher never taught us that - you couldn't elaborate on the formula though oculd you please, it looks confusing what to do.

Ok. If you have money in the bank and you are getting say 5% interest a year and you start with £1000 the following pattern occurs:

After...
1st Year: £1000 x 1.05

2nd Year: (£1000 x 1.05) x 1.05

3rd Year: (£1000 x 1.05 x 1.05) x 1.05

4th Year: (£1000 x 1.05 x 1.05 x 1.05) x 1.05

etc.

The Red Values show the value of the previous year.

This can be simplified to: Amount x (1.05 ^ No. of years)

The tricky bit is working out that 1.05 number. But you'll soon get the hang of it. It is just (100 + Percentage change/100)

Hope that makes it clearer.

Reply 9

Spy_Lord

7

mockel

Click 'Manage Attachments' button in the 'Additional Options' section when posting a message

Hey thanks a lot!

gemma

Oh thanks, our teacher never taught us that - you couldn't elaborate on the formula though oculd you please, it looks confusing what to do.

Well samdavyson explained it pretty well I think. You just need to plug in values really. So if its lets say 7% a year, and you put in £2000, after 6 years you will have:

Total = 2000*(1+7/100)^6= about £3001.

Of course, there's no shame in working through it the long way - thats what I did in my mocks when I hadn't learnt this and had some time to spare :biggrin:

.

Reply 10

Spy_Lord

Hey thanks a lot!

Well samdavyson explained it pretty well I think. You just need to plug in values really. So if its lets say 7% a year, and you put in £2000, after 6 years you will have:

Total = 2000*(1+7/100)^6= about £3001.

Of course, there's no shame in working through it the long way - thats what I did in my mocks when I hadn't learnt this and had some time to spare :biggrin:

.

Thank you loads, that has helped me lots. I always do the long way! I feel stupid now, as this is fairly simple. I understand it fully. I am going through everything that i don't understand. I know alot of it now. :smile:

Thanks again.

Reply 11

john !!

14

Treat them as equals signs. eg.

5x < 2x + 3
3x < 3
x < 1

But remember if you multiply of divide both sides by a negative number you MUST reverse the sign.

eg.

-2x + 5 > 1
2x - 5 < -1
2x < 4
x < 2

Reply 12

how would i rearrange y= 4x/ x +2 to make X the subject?

y= 4x/ x +2

Take the denominator over and multiply by y:

xy+2y=4x

Take 4x to the other side, and 2y to the other side as well:

xy-4x=-2y

Now's the tricky bit, take out x as a common factor:

x(y-4)=-2y

The divide the other side by (y-4)

x=-2y/y-4

If I made any stupid mistakes . . yeesh. :frown:

Reply 14

No, that looks right.

People often forget the factorising. Though it is totally necessary.

Reply 15

john !!

14

y = 4x/(x+2)
yx + 2y = 4x
yx - 4x = -2y
x (y - 4) = -2y
x = -2y/(y-4)

Just get rid of all the denominators then gather all terms of one variable to one side then factorise by taking that variable out, and divide by the factor to leave x on its own.

Reply 16

Spy_Lord

y= 4x/ x +2

Take the denominator over and multiply by y:

xy+2y=4x

Take 4x to the other side, and 2y to the other side as well:

xy-4x=-2y

Now's the tricky bit, take out x as a common factor:

x(y-4)=-2y

The divide the other side by (y-4)

x=-2y/y-4

If I made any stupid mistakes . . yeesh. :frown:

Thank you that makes so much sense....although i don't think i could do it in an exam! Have you got any tips on what to do? Is it just trying to get the X out as much as possible by multilpying and dividin bla bla

Reply 17

Bigfooty

OP

Hi my question is List all the solutions of the inequality 4<2n<=11 where n is an integer - if anybody knows how to do this I will very grateful Cheers :smile:

Reply 18

Bigfooty

Hi my question is List all the solutions of the inequality 4<2n<=11 where n is an integer - if anybody knows how to do this I will very grateful Cheers :smile:

Divide through by 2:

2 < n <= 5.5

Therefore interger values are: 3, 4 and 5.

Hope it helps.

Reply 19