Maths homework help please?

[confusednorthner]

Daughter has just produced this due in tomorrow and she's stuck. I couldn't do this 30 years ago and still can't!

Which bits is she stuck on

What is she stuck on? Re-arranging the equations or plugging the numbers into the equations?

S=vt so to make t the subject you divide each side by v so t = s/v

V=RI to get R you divide each side by I
R=V/I

The whole thing!!

You can get number 3 using the same principle

It’s quite complex to try and explain all of these questions without knowing what exactly your daughter does or doesn’t understand. Perhaps we can support you working through it question by question and help you with what she is stuck on.

You need to get the letter they want the subject to be to be in it's own ie t=s/v

To do this you need to do the same thing on each side. So you started with s=tv which means s=t multiplied by v.

To remove the v on the right hand side divide it by v. So you have to do the same on the other side which brings you to s/v=t

Write that the other way round and you have t as the subject.

Does that make any sense?

When you cross the equals sign the operation reverses, so a multiply becomes a divide and a square becomes a square root.

In the first example you are moving the v to get t on its own, so t = s/v.

There will be YouTube videos on rearranging equations which will be much more useful than reading it on here.

V= u + at - minus 'at' from each side to get what u is
U = v - at

She's got to number 3 and is now FaceTimeing a friend, we will look on you tube . Thanks all, first time homework has stumped me!

To rearrange an equation you need to do the opposite operation when you move a symbol across from one side of the = to the other.
Sometimes it is easier to see with numbers
E.g. For the first one if it said 30=65 but wanted you to make 6 the subject then you need to split the 6 and 5. They are currently multiplied so the opposite is division
30/5=6
So if they were letter A=bc
A/c=b makes b the subject or
A/b=c makes c the subject

Right. She really shouldn't be stuck with the whole thing. It's the same principle repeated over and over. If she can't do it then that means she doesn't understand this work at all. There is no point in getting the answer from mumsnet.

She needs to go in and speak with the teacher. Explain that she just doesn't understand and can she have some help one on one to explain it.

V= E + RI
Minus RI from each side to get E
V- RI = E
E= V - RI

Does she understand that ‘make t the subject’ just means rearranging the equation to find what t equals etc? And that what you do to one side you have to do to the other? I think if she doesn’t understand rearranging equations at all, she needs to take this back to the teacher. She’ll gain nothing if we do it for her on a Sunday night.

'Make A the subject of' means rearrange the equation to be A=…..

Presumably she has done basic algebra in maths so solving for x.
'Making the subject of' is just the same techniques but keeping all the letters.
It is like old fashioned balance scales, whatever she does on one side she has to do on the other.
So s=vt, you want to divide the RHS by v so you divide the LHS by v too -> s/v=t then swap the sides over to get t=s/v

She told teacher she didn't understand and he told her to keep going! She didn't want answers just a point in right direction of understanding.

It's the same questions repeated.

Fairly straightforward.

If she doesn't understand. She needs to look up rearranging formulae.

Bit she would have covered that in lessons, surely?

For the ‘simple’ equations here using triangles can help. (See pic) to make any particular part the ‘subject’ of the formula means putting that part before the equals sign.

In the triangle you can cover the letter you want as the subject and the rest of the triangle is the rest of the formula.

I think the key thing is to remember you need to do the same thing to both sides , and aim to get the thing you want on its own, remembering the first rule.

So S = vt

Divide both sides by v because VT/v = t

So s/v = t

And then V = u + at

Take away at from both:

V - at = u + at - at = u

Or if you wanted to get t instead:

You would take away u first to get the "lump" with the t in on its own.

So v-u = at

Then divide by a to get rid of the a

So (v-u)/a = t

It's a pretty hard concept to teach only in writing though. If she's stuck, I would get her to do her best, write her a note and take it back to the teacher to go through. Preferably before it's due in.

Number 6 is more complex to get I
V = E + RI
RI = V- E
I = V-E / R (so V-E divided by R)

For example if you cover up the s you get vt meaning s=vt (which is what you’ve been given.

If you cover up t which question 1a wants you to have as the subject you are left with s over v

Are we helping at all?

Yeah, a bit of thanks for those trying to help wouldn't go amiss!

Tell her to think of it as a set of scales.
Each side balances.
So if you take 3 from one side , you have to take 3 from the other side as tell....
If you times one side by 2 you have to times the other side as well ....