# having difficulties with Geometric series question

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Thread starter 4 years ago
#1
Q:

Please note I am having problems with the first part only.
I tried my best to answer it. I have attached it.

The problem I have is with the worked solutions is how did the author come up with
:

I thought that
therefore r = common ratio =

and lastly how did the author need up with where as the answer

I thought is wrong.
Shouldn't ?
Please if someone can be kind to explain to me thank you

Edit: Please don't worry about the second part of the question
I did this question

the author's solution has been added
0
4 years ago
#2
(Original post by bigmansouf)
The problem I have is with the worked solutions is how did the author come up with:
No idea - just looks wrong.

I thought that
therefore r = common ratio =
I assume you meant that to continue, rather than stop at

If so, then agreed.

Though in your subsequent working you should have 1-(1/r) in the denominator, not 1-r.

and lastly how did the author need up with where as the answer

I thought is wrong.
Shouldn't ?
Please if someone can be kind to explain to me thank you
Looks like another error in the book
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Thread starter 4 years ago
#3
(Original post by ghostwalker)
No idea - just looks wrong.

I assume you meant that to continue, rather than stop at

If so, then agreed.

Though in your subsequent working you should have 1-(1/r) in the denominator, not 1-r.

Looks like another error in the book
its the same book i showed you in the other thread

this is the solution it gave
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4 years ago
#4
(Original post by bigmansouf)
its the same book i showed you in the other thread
I thought it was the same volume.

I stand by my previous post.
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Thread starter 4 years ago
#5
(Original post by ghostwalker)
I thought it was the same volume.

I stand by my previous post.
Sorry i want to ask are you familiar with AEB questions?
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4 years ago
#6
(Original post by bigmansouf)
Sorry i want to ask are you familiar with AEB questions?
Difficult to know, I don't associate any particular questions with AEB - even had to look up what the abbreviation meant.
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Thread starter 4 years ago
#7
(Original post by ghostwalker)
Difficult to know, I don't associate any particular questions with AEB - even had to look up what the abbreviation meant.

AEB - associated examining board

I wanted to ask about questions like this:
The ninth term of an arithmetic progression is 52 and the sum of the first twelve terms is 414. Find the first term and common difference. The rth term of an arithmetic progression (1+4r). Find, in terms of n, the sum of the first n terms of the progression.

The point i wanted to make is the The rth term of an arithmetic progression (1+4r). part. From your opinion do you think that this part is added to distract or confused students.
0
4 years ago
#8
(Original post by bigmansouf)
AEB - associated examining board

I wanted to ask about questions like this:
The ninth term of an arithmetic progression is 52 and the sum of the first twelve terms is 414. Find the first term and common difference. The rth term of an arithmetic progression (1+4r). Find, in terms of n, the sum of the first n terms of the progression.

The point i wanted to make is the The rth term of an arithmetic progression (1+4r). part. From your opinion do you think that this part is added to distract or confused students.
I would take this to be two different questions, or two parts of a question dealing with two different series.

From the way you've written it, it looks to be one, but that may just be how you've written it.

Can you link/scan/photo the original?
0
4 years ago
#9
(Original post by ghostwalker)
I thought it was the same volume.

I stand by my previous post.
To be brutally honest, it doesn't look like the author should be writing books about mathematics!
1
Thread starter 4 years ago
#10
(Original post by ghostwalker)
I would take this to be two different questions, or two parts of a question dealing with two different series.

From the way you've written it, it looks to be one, but that may just be how you've written it.

Can you link/scan/photo the original?
number Q 25 thank you
0
4 years ago
#11
(Original post by bigmansouf)
number Q 25 thank you
This material is a reworked copy of the original, and, IMO, has lost a bit in transcription. It's not designed to confuse or trick you.

Can't get hold of the original paper, but I would think this question was originally split into two parts, and it certainly refers to two different APs.
0
4 years ago
#12
(Original post by DFranklin)
To be brutally honest, it doesn't look like the author should be writing books about mathematics!
Agreed. Out of interest I tracked down the publishers. It's a private limited company with two shareholders. No prizes for guessing who the company director is!

Didn't realise vanity publishing extended to the academic sector - perhaps I'm being a bit mean there....
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Thread starter 4 years ago
#13
(Original post by ghostwalker)
Agreed. Out of interest I tracked down the publishers. It's a private limited company with two shareholders. No prizes for guessing who the company director is!

Didn't realise vanity publishing extended to the academic sector - perhaps I'm being a bit mean there....
(Original post by DFranklin)
To be brutally honest, it doesn't look like the author should be writing books about mathematics!
thank you very much
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