Geometric analysis

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50ShadesOfRay
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#1
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#1
Estimates are produced for the number of babies born worldwide each year. The estimates for 2004 and 2008, given in thousands of births to the nearest thousand, were 130,350 and 137,804 respectively. Assume that successive yearly estimates are in a geometric progression.

The anual increase in births between 2004 & 2008 is 1.43%




Find the estimates for 2006 and 2011 (to the nearest thousand)


when estimating 2011 is it

(100+(1.43*7))%x130,350 = 143398.035

the answer given is 144000

surely the answer is wrong seeing as to the nearest thousand its 143000?
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TenOfThem
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#2
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#2
(Original post by 50ShadesOfRay)
Estimates are produced for the number of babies born worldwide each year. The estimates for 2004 and 2008, given in thousands of births to the nearest thousand, were 130,350 and 137,804 respectively. Assume that successive yearly estimates are in a geometric progression.

The anual increase in births between 2004 & 2008 is 1.43%




Find the estimates for 2006 and 2011 (to the nearest thousand)


when estimating 2011 is it

(100+(1.43*7))%x130,350 = 143398.035

the answer given is 144000

surely the answer is wrong seeing as to the nearest thousand its 143000?
Everything in red is incorrect

The answer is 143673 so is 144000 to the nearest thousand
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50ShadesOfRay
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#3
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#3
(Original post by TenOfThem)
Everything in red is incorrect

The answer is 143673 so is 144000 to the nearest thousand

The 1.43% is definitely correct.
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TenOfThem
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#4
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#4
(Original post by 50ShadesOfRay)
The 1.43% is definitely correct.
No it isn't

130350 x 1.0143^4 is not 137804
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50ShadesOfRay
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#5
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#5
(Original post by TenOfThem)
No it isn't

130350 x 1.0143^4 is not 137804
no the annual increase is 1.43%

the increase over four years is 5.72%
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TenOfThem
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#6
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#6
(Original post by 50ShadesOfRay)
no the annual increase is 1.43%

the increase over four years is 5.72%
Perhaps you could explain where you get that value from?

The 4th root of 1.05718 is not 1.0143

Oh, I see - you divided by 4 - that is not correct
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50ShadesOfRay
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#7
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(Original post by TenOfThem)
Perhaps you could explain where you get that value from?

The 4th root of 1.05718 is not 1.0143

Oh, I see - you divided by 4 - that is not correct
MPM1(21)sigma.pdf

here is an attachment to the homework, it is q11, and the answers are listed below q12
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TenOfThem
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#8
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#8
(Original post by 50ShadesOfRay)
MPM1(21)sigma.pdf

here is an attachment to the homework, it is q11, and the answers are listed below q12
I understood the question and I know what the answers are as I have worked them out

It is you who are not doing the correct calculations
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50ShadesOfRay
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#9
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#9
(Original post by TenOfThem)
I understood the question and I know what the answers are as I have worked them out

It is you who are not doing the correct calculations

so they've given me the wrong answers?
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TenOfThem
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#10
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#10
(Original post by 50ShadesOfRay)
so they've given me the wrong answers?
no the answers given are fine
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50ShadesOfRay
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#11
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#11
(Original post by TenOfThem)
no the answers given are fine
the answer given is 1.4%... I am right?
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TenOfThem
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#12
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#12
(Original post by 50ShadesOfRay)
the answer given is 1.4%... I am right?
The answer is 1.4% to 1dp, yes

Your answer of 1.43% is incorrect
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50ShadesOfRay
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#13
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#13
(Original post by TenOfThem)
The answer is 1.4% to 1dp, yes

Your answer of 1.43% is incorrect

i obviously don't know what i'm doing then, forget it, thanks anyway
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TenOfThem
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#14
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#14
(Original post by 50ShadesOfRay)
i obviously don't know what i'm doing then,
Indeed

Did you read post 6 where I told you exactly what your error was?
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50ShadesOfRay
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#15
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#15
(Original post by TenOfThem)
Indeed

Did you read post 6 where I told you exactly what your error was?
why is dividing by 4 incorrect though, it's from 2004 to 2008 that's 4 years?
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TenOfThem
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#16
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#16
(Original post by 50ShadesOfRay)
why is dividing by 4 incorrect though, it's from 2004 to 2008 that's 4 years?
Because a geometric progression involves powers of the ratio, not multiples of the ratio

So you need the 4th root, not divide by 4
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50ShadesOfRay
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#17
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#17
(Original post by TenOfThem)
Because a geometric progression involves powers of the ratio, not multiples of the ratio

So you need the 4th root, not divide by 4
are you saying the fourth root of 5.72%?
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TenOfThem
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#18
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#18
(Original post by 50ShadesOfRay)
are you saying the fourth root of 5.72%?
No

The 4th root of 1.05718

Do you understand how geometric progressions work

I assume that you did he 2008 value divided by the 2004 value and you had 1.05718

So that means

2004 x ? x ? x ? x ? = 2008

so ?^4 = 1.05718
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50ShadesOfRay
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#19
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#19
(Original post by TenOfThem)
No

The 4th root of 1.05718

Do you understand how geometric progressions work

I assume that you did he 2008 value divided by the 2004 value and you had 1.05718

So that means

2004 x ? x ? x ? x ? = 2008

so ?^4 = 1.05718
is it 1.3999% ?
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TenOfThem
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#20
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#20
(Original post by 50ShadesOfRay)
is it 1.3999% ?
Yes
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