can someone post the link to the gcse olevels timetable OCT/NOV 2012

[aalmuhannadi]

Well, I got it!
As it's written S=3/t-2
First take t-2 on the left hand side
and take 'S' to the denominator that will be t-2=3/s
so, to make the t the subject, -2 will be converted in +2 and take it to the right hand side
t=3/s+2

We seem to have different answers?

 

[zainabkhann]

Well, I got it!
As it's written S=3/t-2
First take t-2 on the left hand side
and take 'S' to the denominator that will be t-2=3/s
so, to make the t the subject, -2 will be converted in +2 and take it to the right hand side
t=3/s+2

Why isnt the +2 added to the 3 like this: t=3+2/s ?

 

[zainabkhann]

s = 3 / t-2
We need to make t the subject of the formula.
First of all, multiply both sides by 't-2' in order to get rid of the fraction
Then we have s(t-2) = 3
Simplify it to ts - 2s = 3
Add 2s to both sides in order to have ts on its own: ts = 3 + 2s
Then divide both sides by s in order to get t on its own: t = 3 + 2s / s

Your right i jus checked the book

 

[zainabkhann]

Your right i jus checked the book

That was really easy btw, i just dont know when to like get rid of the fraction, because every question regarding this topic is different from the other, so its hard to grasp the concept.

 

[aalmuhannadi]

That was really easy btw, i just dont know when to like get rid of the fraction, because every question regarding this topic is different from the other, so its hard to grasp the concept.

Well I'd be glad to help if you have any more examples?

 

[zainabkhann]

yeah paper 1, year 1996 question 2:

Make x the subject of the formula
y=A+2x/x

 

[aalmuhannadi]

yeah paper 1, year 1996 question 2:

Make x the subject of the formula
y=A+2x/x

Hmm I'm not sure but can you check in the answer sheet if it's x = (y - A) / 2? Not sure of it but can't hurt to check

 

[zainabkhann]

Hmm I'm not sure but can you check in the answer sheet if it's x = (y - A) / 2? Not sure of it but can't hurt to check

Its x= A/y-2

 

[zainabkhann]

Guys, please check this pdf again and turn to page 4 where there is variations, it says direct proportion: y=kx only, it doesnt say y=kx^2, howcome?

thanks

 

[zainabkhann]

theres a quesiton in variations which says:

sixteen workers can build a wall in 25 days
how many workers are needed if the wall has to be built in 10 days?

I dont understand the solution process in the book so can anyone explain it in a better way. thanks

 

[aalmuhannadi]

theres a quesiton in variations which says:

sixteen workers can build a wall in 25 days
how many workers are needed if the wall has to be built in 10 days?

I dont understand the solution process in the book so can anyone explain it in a better way. thanks

16 workers : 25 days
x workers : 10 days

How do you get from 25 to 10? you divide 25 by 2.5.
Divide 16 by 2.5 to get 6.4.

 

[zainabkhann]

16 workers : 25 days
x workers : 10 days

How do you get from 25 to 10? you divide 25 by 2.5.
Divide 16 by 2.5 to get 6.4.

But the answer is 40 workers, Its a variations question btw, you need to use the inversly propotional formula.
y=k/x

In thinking process it says that note : the no. of workers indirectly propotional to the number of days needed, so how did they come up with that, why is it not directly propotional?

 

[aalmuhannadi]

But the answer is 40 workers, Its a variations question btw, you need to use the inversly propotional formula.
y=k/x

In thinking process it says that note : the no. of workers indirectly propotional to the number of days needed, so how did they come up with that, why is it not directly propotional?

Oh sorry, I mistook the question. It is indirectly proportional because the more workers you have, the less days needed to construct the wall. And similarly, the less workers you have, the more days it takes for the wall to be complete. Inversely proportional means that if one increases, the other decreases, or if one decreases, the other increases.

Remember the y = k / x formula. 25 = k / 16
k = (25 X 16) = 400.

Substitute 10 for x.
y = 400 / 10 = 40 workers.

 

[zainabkhann]

Oh sorry, I mistook the question. It is indirectly proportional because the more workers you have, the less days needed to construct the wall. And similarly, the less workers you have, the more days it takes for the wall to be complete. Inversely proportional means that if one increases, the other decreases, or if one decreases, the other increases.

Remember the y = k / x formula. 25 = k / 16
k = (25 X 16) = 400.

Substitute 10 for x.
y = 400 / 10 = 40 workers.

Oh thats a good thing to point out. thanks that helped alot. im going to try another question with this concept and check if i get the right answer.. Going to post another question from the topic which is bothering me in a minute k

 

[zainabkhann]

Oh thats a good thing to point out. thanks that helped alot. im going to try another question with this concept and check if i get the right answer.. Going to post another question from the topic which is bothering me in a minute k

What defination would you give direct proportional btw ?

 

[aalmuhannadi]

What defination would you give direct proportional btw ?

Direct proportionality is exactly the opposite; it's when one thing increases and the other thing has to increase with it, or if one thing decreases the other thing also has to decrease with it.

 

[zainabkhann]

Okey i got the right answer to another similar question, theres another question here which says:
force of newton: F
distance: D

when the magnets are at a certain distance apart, the force is 10 N
what is the force when the distance is doubled?

Please explain

 

[aalmuhannadi]

Okey i got the right answer to another similar question, theres another question here which says:
force of newton: F
distance: D

when the magnets are at a certain distance apart, the force is 10 N
what is the force when the distance is doubled?

Please explain

Is it 5N?

 

[zainabkhann]

no its a very weird answer in the book. let me try to write it down

ans: k/(2d)^2 = k/4d^2
When the distance is doubled, the force is 40 Newtons.

 

[aalmuhannadi]

no its a very weird answer in the book. let me try to write it down

ans: k/(2d)^2 = k/4d^2
When the distance is doubled, the force is 40 Newtons.

Oh.. Don't know what happened there sorry :/ I didn't do O-Levels so I don't know exactly what the syllabus contains, maybe that's a different topic?