OCR MEI Numerical Methods 12th June 2015

Original post by Genty Boy

Mark scheme disagrees with you.

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i know thats why its confusing. the books wrong

Reply 23

Genty Boy

3

Original post by runny4

i know thats why its confusing. the books wrong

I never use books when revising, doing past papers is the best way to get a good understanding.

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Reply 24

for june 2013 7v, why can't u give 61.80114905 as ur answer because it says s100 is exact and s200 is exact and it says the error which u have to assume is 0.046 so if anything the final answer should be to 2sf?

Reply 25

for june 2012, question 6iii,
why does it say this 'Since the integral is over a range of 2 units the correct value will lie within ± 0.000 01 of the value given previously'
I mean i get that there is an error in the range ± 0.000 005 in each value becuase the data is rounded but the other thing makes no sense?

Reply 26

For january 2009 question 2iib,
why is a value with more sig fig more accurate because if u did something like 1-0.5 it would equal 0.5 and it would be 100% accurate even though it has one sig fig
Also in the mark scheme it says Subtraction of nearly equal quantities loses precision- im wondering is accuracy and precision the same?

Reply 27

on june 2008- question 7ii the examiners report says
The iterative formula given is in the form of a square root. The correct comment was that a square root is, by definition, positive so it cannot give a negative answer.
but then why is the square root of 25 , five and -5?

Reply 28

OP

Original post by runny4

on june 2008- question 7ii the examiners report says
The iterative formula given is in the form of a square root. The correct comment was that a square root is, by definition, positive so it cannot give a negative answer.
but then why is the square root of 25 , five and -5?

Because (-5)^2 = 25
The root can be -ve it's what's being rooted that can't be -ve

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Reply 29

also for convergence i know the gradient has to be between 1 and -1 but on last years paper there was a question which said a value close to one indicates slow convergence. does that mean 0 has the fastest convergence?

Reply 30

Original post by Leechayy

Because (-5)^2 = 25
The root can be -ve it's what's being rooted that can't be -ve

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on the examiners report it says
The iterative formula given is in the form of a square root. The correct comment was that a square root is, by definition, positive so it cannot give a negative answer. A common incorrect comment was that it is impossible to take the square root of a negative quantity.

Reply 31

also for june 2013, question 6iii, it says
that both the trapezium and midpoint rule have 2nd order convergence
but in the textbook it says
absolute error in t/m 2 divided by the absolute error in t/m 1 is equal to 0.25 so they said t1,t2,t4.... have first order convergence with k=0.25 although they also said that they are second order methods as the absolute error in each is proportional to h^2.

Reply 32

Bruhh

10

Not looking forward to this, most questions are fairly straight forward just the odd few to catch you out. Lost all motivation since everyone else has finished and we're now back at school :frown:

Reply 33

in january 2008, question 7v, the examiners report says
In the final section the two required features of a spreadsheet were that it works to greater accuracy – i.e. a greater number of significant figures – than the simple computer program, and that it does not display all the significant figures that it uses. The second point was appreciated by only a few. The existence of “guard digits” in computer software and in calculators is an important point – and it is quite distinct from working to a large number of significant figures
how is it distinct?

Reply 34

OP

Original post by runny4

on the examiners report it says
The iterative formula given is in the form of a square root. The correct comment was that a square root is, by definition, positive so it cannot give a negative answer. A common incorrect comment was that it is impossible to take the square root of a negative quantity.

I had a look at the question and the question itself is based on proving that there is only one root.
Once you do that, in part (ii), it says that the equation has 2 -ve roots but the iterated equation is a rearrangment of a function with only one root.
Therefore, it'll only present +ve values.

At least, that's what I can make out of it.
It's a really gimmicky question, sorry if I am unclear

Reply 35

for january 2007, question 3, why wouldn't u use the ratio of 0.36 because both ratios agree to this value.- surely this more accurate than using the last one.

Reply 36

Original post by Leechayy

I had a look at the question and the question itself is based on proving that there is only one root.
Once you do that, in part (ii), it says that the equation has 2 -ve roots but the iterated equation is a rearrangment of a function with only one root.
Therefore, it'll only present +ve values.

At least, that's what I can make out of it.
It's a really gimmicky question, sorry if I am unclear

thanks

Reply 37

OP

Original post by runny4

thanks

Yw

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Reply 38

Bruhh

10

Can anyone give me a link to last years past paper and mark scheme please?

Edit: found one here for anyone else looking: http://vle.woodhouse.ac.uk/topicdocs/maths/PastPapersfile/NM2014May.pdf

(edited 8 years ago)

Reply 39

OP