Can someone please explain, what to think/ do when writing an expression?
For example for this question.
I have wrote
Ali
3 more
2 hours less
72 components
Beth
72 components
How do I write the expression. (part i)
And then please can you go through the rest of the question.
Once I understand what to think, when writing an expression and learn how to do the other parts, it will be a lot more simple!
Question attached
Thanks
Writing expressions??! How? (3 marks)

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 1
 05052012 19:12

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 2
 05052012 22:48
Ali makes 72 components in t hours
to show how many he makes in 1 hour divide by t
ie 72/t components in t/t = 1 hour
Beth makes 72 components in t+2 hours
divide by t+2
that should get you startedLast edited by sputum; 05052012 at 22:49. 
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 3
 05052012 22:48
(i) Number per hour = Number/time
N_{a} = ^{72}/_{t}
For N_{b} you need to change t to t+2 as Beth takes 2 hours longer
Then N_{b} + 3 = N_{a} and rearrange 
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 4
 05052012 22:57
(Original post by blueray)
Can someone please explain, what to think/ do when writing an expression?
For example for this question.
I have wrote
Ali
3 more
2 hours less
72 components
Beth
72 components
How do I write the expression. (part i)
And then please can you go through the rest of the question.
Once I understand what to think, when writing an expression and learn how to do the other parts, it will be a lot more simple!
Question attached
Thanks
t the time for Ali to make 72
then the component per hour
72/t
For Beth
the components per hour
72/t 3 (3 less per hour) 
 Follow
 5
 05052012 23:04
It has all been explained this question... spo I hope that is enough for you.
(Original post by blueray)
Can someone please explain, what to think/ do when writing an expression?
For example for this question.
I have wrote
Ali
3 more
2 hours less
72 components
Beth
72 components
How do I write the expression. (part i)
And then please can you go through the rest of the question.
Once I understand what to think, when writing an expression and learn how to do the other parts, it will be a lot more simple!
Question attached
Thanks 
 Follow
 6
 05052012 23:08
(Original post by ztibor)
i)
t the time for Ali to make 72
then the component per hour
72/t
For Beth
the components per hour
72/t 3 (3 less per hour) 
 Follow
 7
 06052012 12:23
(Original post by sputum)
Ali makes 72 components in t hours
to show how many he makes in 1 hour divide by t
ie 72/t components in t/t = 1 hour
Beth makes 72 components in t+2 hours
divide by t+2
that should get you started
(Original post by TenOfThem)
(i) Number per hour = Number/time
N_{a} = ^{72}/_{t}
For N_{b} you need to change t to t+2 as Beth takes 2 hours longer
Then N_{b} + 3 = N_{a} and rearrange
(Original post by ztibor)
i)
t the time for Ali to make 72
then the component per hour
72/t
For Beth
the components per hour
72/t 3 (3 less per hour)
(Original post by GreenLantern1)
It has all been explained this question... spo I hope that is enough for you.
why not 72/t2 Because it takes him 2 hours less???
Where am I wrong? Please explain. 
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 8
 06052012 12:24
(Original post by blueray)
Why would ali be 72/t
why not 72/t2 Because it takes him 2 hours less???
Where am I wrong? Please explain. 
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 9
 06052012 12:27
(Original post by TenOfThem)
t was defined in the question as the time that Ali takes 
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 06052012 12:49
(Original post by blueray)
Ok So when would I be correct then, what would the question have to say, for my answer to be correct? 
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 11
 06052012 13:53
(Original post by sputum)
Ali makes 72 components in t hours
to show how many he makes in 1 hour divide by t
ie 72/t components in t/t = 1 hour
Beth makes 72 components in t+2 hours
divide by t+2
that should get you started
(Original post by ztibor)
i)
t the time for Ali to make 72
then the component per hour
72/t
For Beth
the components per hour
72/t 3 (3 less per hour)
(Original post by GreenLantern1)
It has all been explained this question... spo I hope that is enough for you.
(Original post by TenOfThem)
Beth takes longer
What does derive mean? How do I do it? 
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 06052012 14:00
I gave you 3 equations in post 3
combine them
rearrange 
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 13
 06052012 14:08
(Original post by blueray)
?
The number of components that Beth makes per hour is 72/t+2.
Ali makes 3 more per hour, so
So,
Now multiply all the numerators by (t) and (t+2) to get:
This is equalise same as:
Multiply out your brackets to get
This help?
EDIT: to figure out part iii) multiply out your brackets in the last equation, and rearrange to get a quadratic, then figure out your values of t from thereLast edited by CharlieBoardman; 06052012 at 14:13. 
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 14
 06052012 14:13
(Original post by CharlieBoardman)
Right, so the number of components that Ali makes per hour is 72/t
The number of components that Beth makes per hour is 72/t+2.
Ali makes 3 more per hour, so
So,
Now multiply all the numerators by (t) and (t+2) to get:
This is equalise same as:
Multiply out your brackets to get
This help?
But thing I can't get my head round is
if Ali makes 3 MORE then why is +3 with Beth??
Shouldn't it be
72/t +3 = 72/t+2 ??
Then 72/t  72/t+2 = 3??????/ 
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 15
 06052012 14:19
(Original post by blueray)
All the steps are well done thanks
But thing I can't get my head round is
if Ali makes 3 MORE then why is +3 with Beth??
Shouldn't it be
72/t +3 = 72/t+2 ??
Then 72/t  72/t+2 = 3??????/
Components of Ali per hour = 72/t
Components of Beth per hour = 72/t+2 yes?
Right, so Ali makes 3 more than Beth per hour, so 72/t is 3 more than 72/t+2. So to make them equal, you need to add 3 onto 72/t+2, giving you the 72/t=(72/t+2)+3
This explain it ok? 
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 16
 06052012 14:22
(Original post by CharlieBoardman)
I see where your confusion comes from look at it this way.
Components of Ali per hour = 72/t
Components of Beth per hour = 72/t+2 yes?
Right, so Ali makes 3 more than Beth per hour, so 72/t is 3 more than 72/t+2. So to make them equal, you need to add 3 onto 72/t+2, giving you the 72/t=(72/t+2)+3
This explain it ok?
Ps I have lots of English literature notes etc, if you want 
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 17
 06052012 14:29
(Original post by blueray)
Yeah that makes sense, but why would you want to make them equal? Sorry if I sound silly, I just want to be crystal clear
Ps I have lots of English literature notes etc, if you want
For example. We used 72/t=(72/t+2)+3, which we could rearrange to get us somewhere.
72/t=72/t or 72/t+2=72/t+2 would have been useless to us.
This ok?
What books are you studying for Lit? 
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 18
 06052012 14:31
(Original post by blueray)
Yeah that makes sense, but why would you want to make them equal?
How would you end up with an equation if you did not have 2 things that were equal to each other 
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 06052012 14:33
(Original post by TenOfThem)
How would you end up with an equation if you did not have 2 things that were equal to each other 
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 20
 06052012 14:36
(Original post by CharlieBoardman)
I see where your confusion comes from look at it this way.
Components of Ali per hour = 72/t
Components of Beth per hour = 72/t+2 yes?
Right, so Ali makes 3 more than Beth per hour, so 72/t is 3 more than 72/t+2. So to make them equal, you need to add 3 onto 72/t+2, giving you the 72/t=(72/t+2)+3
This explain it ok?
(Original post by CharlieBoardman)
What books are you studying for Lit?
(Original post by TenOfThem)
How would you end up with an equation if you did not have 2 things that were equal to each other
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Updated: May 6, 2012
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