Homework time - Algebra - please help

[Slyjoe]

My lad has an Algebra question - I'm i'm too rusty to remember how to do it! Please help and explain.
Petra and Ed have different amounts of money in whole pounds.
Petra=x
Ed=y

Petras amount times 4, then subtract five = Eds amount.
Multiply Petras amount by 3 then add 5 = twice Eds amount.

Wtf? = x and y?

[Percy Flage]

It's been many years, but I think.....

4x-5=y
3x+5=2y

You can eliminate the 5s

Therefore 7x = 3y

Which makes x = 3 and y = 7.

Test it...
4x3=12-5=7
3x3=9+5=14.

Edited by Percy Flage on Saturday 25th April 11:37

[NiceCupOfTea]

it's a simultaneous equation isn't it?

[blank]

Percy Flage said:

It's been many years, but I think.....

4x-5=y
3x+5=2y

You can eliminate the 5s

Therefore 7x = 3y

Which makes x = 3 and y = 7.

Test it...
4x3=12-5=7
3x3=9+5=14.

Edited by Percy Flage on Saturday 25th April 11:37

That answer's correct but it's an odd way to do it!

From 7x=3y, x and y could also be 6 and 14. Or any multiple of 3 and 7, because you have 1 equation with 2 variables.

The full way to do it is:

Eq 1: 4x-5=y
Eq 2: 3x+5=2y

You need to eliminate one of the variables by adding or subtracting the equations from each other. So the first thing to do is to get 2y in Eq 1 - multiply it all by 2.

Eq 1a: 8x-10=2y

Then if you do Eq 1a minus Eq 2:

5x-15=0 - no ys left

Re-arrange and solve:

5x=15
x=15/5
x=3

Put that back into one of the other equations (I'll use Eq 1)

4x-5=y
12-5=y
y=7

[Slyjoe]

Wow - thanks guys -My boy is in his final few weeks of PRIMARY school, Lord only knows how they expected him to work this baby out.

[Norbury90]

I always did silumtaneous equations in my head, so much easier IMO. I would get the answer, and then have to work my way through writing down the equation...

[Flanders.]

I don't feel thick atall.

[ShadownINja]

Slyjoe said:

Wow - thanks guys -My boy is in his final few weeks of PRIMARY school, Lord only knows how they expected him to work this baby out.

Primary school?? I'm impressed. Isn't this stuff supposed to be A level standard now?

[Slyjoe]

ShadownINja said:

Slyjoe said:

Wow - thanks guys -My boy is in his final few weeks of PRIMARY school, Lord only knows how they expected him to work this baby out.

Primary school?? I'm impressed. Isn't this stuff supposed to be A level standard now?

To be fair his homework consisted of a lot of questions that were of a similar difficulty, which he handled without a problem, or assistance. It was just this one that stumped the pair of us.
Guess I'm going to be re-learning a lot more stuff over the coming years.

[wulluff]

NiceCupOfTea said:

it's a simultaneous equation isn't it?

I was away the day they taught simultaneous equations. Mind you that was a very long time ago and i've never needed them

Edited by wulluff on Saturday 25th April 18:04

[ShadownINja]

Slyjoe said:

ShadownINja said:

Slyjoe said:

Wow - thanks guys -My boy is in his final few weeks of PRIMARY school, Lord only knows how they expected him to work this baby out.

Primary school?? I'm impressed. Isn't this stuff supposed to be A level standard now?

To be fair his homework consisted of a lot of questions that were of a similar difficulty, which he handled without a problem, or assistance. It was just this one that stumped the pair of us.
Guess I'm going to be re-learning a lot more stuff over the coming years.

I wasn't criticising. Genuinely impressed that he's doing this kind of thing.

And yes, you will be studying a lot over the next few years. I hope you liked school the first time round.

[james_gt3rs]

ShadownINja said:

Slyjoe said:

Wow - thanks guys -My boy is in his final few weeks of PRIMARY school, Lord only knows how they expected him to work this baby out.

Primary school?? I'm impressed. Isn't this stuff supposed to be A level standard now?

It's on the GCSE higher paper, one of the hardest things on the paper.

It's a also basic A level maths skill you learn in the first month of A levels.

[ShadownINja]

This is what I thought.

[Slyjoe]

ShadownINja said:

Slyjoe said:

ShadownINja said:

Slyjoe said:

Wow - thanks guys -My boy is in his final few weeks of PRIMARY school, Lord only knows how they expected him to work this baby out.

Primary school?? I'm impressed. Isn't this stuff supposed to be A level standard now?

To be fair his homework consisted of a lot of questions that were of a similar difficulty, which he handled without a problem, or assistance. It was just this one that stumped the pair of us.
Guess I'm going to be re-learning a lot more stuff over the coming years.

I wasn't criticising. Genuinely impressed that he's doing this kind of thing.

And yes, you will be studying a lot over the next few years. I hope you liked school the first time round.

None taken!
I certainly dont remember it being that hard when I was at Primary - 25 years or so ago.
Its good to know that he's genuinley getting challenging work at his age. Lets just hope he doesn't move on to Media studies or some such other wk.

[ShadownINja]

Is he in a good school? Maybe that's why he's doing it.

[Pow!]

Try this

x(15e -o.2t) in series

[Slyjoe]

ShadownINja said:

Is he in a good school? Maybe that's why he's doing it.

Nope - just a boggo Primary - however, wether it makes any difference or not, I dont know, it is a 100% english school in a nice-ish area - very little ethnic diversity, and very little chav influence.
Guess that just allows them to concentrate on the three R's and not have to worry about knives, drugs, and equality issues.
I'm sure that some primary schools are frickin war-zones.

[ShadownINja]

Slyjoe said:

ShadownINja said:

Is he in a good school? Maybe that's why he's doing it.

Nope - just a boggo Primary - however, wether it makes any difference or not, I dont know, it is a 100% english school in a nice-ish area - very little ethnic diversity, and very little chav influence.
Guess that just allows them to concentrate on the three R's and not have to worry about knives, drugs, and equality issues.
I'm sure that some primary schools are frickin war-zones.

You may well be right!