Arsey's D1 Edexcel revision and resources thread

hi. I have question about the objective line in general.
Basicly i have no idea how it works. If for example say my objective function is minimize = 6x+9y, Then how do i draw a line for it. do i just guess a number?

Reply 41

TheInfidel

1

Original post by Zik007

hi. I have question about the objective line in general.
Basicly i have no idea how it works. If for example say my objective function is minimize = 6x+9y, Then how do i draw a line for it. do i just guess a number?

My teacher told me what you do is times the number together and let it equal that number, in your example;

Minimize = 6x+9y

6x9 = 45

6x + 9y = 45

Can anyone vouch for this method???

Reply 42

forsparta

Original post by Zik007

hi. I have question about the objective line in general.
Basicly i have no idea how it works. If for example say my objective function is minimize = 6x+9y, Then how do i draw a line for it. do i just guess a number?

Rearrange for y, say you had P=6x+9y -> y=1/9 (P-6x) you then draw a line with gradient -6/9=-2/3

Reply 43

Zik007

10

right thanks guys i shall put it to use and see if i am any better than before.

Reply 44

Elliemay97

1

Hi, I have a question about finding the maximum iterations when doing a binary search. I know the list halves at each iteration but I'm not sure whether to round up or down for odd number.
For example if there is 10 in the list it would go 10 5 but after would it be 2 or 3 ??
Thanks

Reply 45

nmanvi

14

Original post by Elliemay97

Hi, I have a question about finding the maximum iterations when doing a binary search. I know the list halves at each iteration but I'm not sure whether to round up or down for odd number.
For example if there is 10 in the list it would go 10 5 but after would it be 2 or 3 ??
Thanks

well you will get 2.5 but that is irrelevant since u do not round till the end (though yes we do round up so we reject the 3rd term not 2nd)

so when we divide by 2 once we get 5, then 2.5, then 1.25 then 0.625 then we stop (as 0.625 < 1)

the max number of iterations is 4 as we divided by 2 four times

----------------------------
method 2 (the one i use)
if you do log base 2 of the number of items in the list, then round it up, you get the answer.
i.e Log2(5) = 3.2......... >>> 4

(edited 9 years ago)

Reply 46

nmanvi

14

Original post by Zik007

hi. I have question about the objective line in general.
Basicly i have no idea how it works. If for example say my objective function is minimize = 6x+9y, Then how do i draw a line for it. do i just guess a number?

Original post by TheInfidel

My teacher told me what you do is times the number together and let it equal that number, in your example;

Minimize = 6x+9y

6x9 = 45

6x + 9y = 45

Can anyone vouch for this method???

Yes this is a good method , the end number should be multiples of the LCM of 6 and 9 (in this case 45).
So if 45 makes the line awkward (i.e its barely on the graph) you can use 90 or 135

This is not mandatory but makes it a lot easier to draw the line, it doesn't matter where you put it as long as the gradient is correct

Reply 47

subject1

18

Grade boundaries for D1 are shockingly high. I mean the paper is accessible, but just make a silly mistake in a question, and that would be 10 marks and a grade!

Reply 48

Hudl

16

I hope Edexcel are a bit more inventive with the D1 paper this year as I do not want the grade boundaries soaring once again this year!

Reply 49

newguy101

8

Hey Arsey, I just wanted to say thanks for all of your forumn threads with the past papers on it and the threads like this one. I've never been a high achiever in Maths but I seem to be doing really good looking at the unofficial mark schemes u put up so far, couldn't have done it without ya dude.

I am pretty sure I got an A in c1, c2 and a high B in M1. Tomorrow I have FP1 and S1 which are both going well and D1 on thursday (which is the one I'm worried about since I always have to rush in D1 because I spend ages just thinking of how to do it and then I slowly begin running out of time until I'm sprinting through the last question).

Nevertheless thanks for the help and hopefully I can get through the next few days :biggrin:

And also did u ever think of making a site like the guy who runs exam solutions? His videos are amazing and maybe you can do it to and earn some $$$$$ :wink:

Just an idea lol.

Reply 50

TheInfidel

1

Original post by newguy101

And also did u ever think of making a site like the guy who runs exam solutions? His videos are amazing and maybe you can do it to and earn some $$$$$ :wink:

Just an idea lol.

Apparently Arsey has a day job :cool:

, i asked him that already.

Original post by Arsey

.....

Do you give me permission to upload your solutions to a website i am making?

(edited 9 years ago)

Reply 51

Saywhatyoumean

10

How do you find the maximum number of interchanges needed to sort a list if six pieces of data using bubble sort??

Posted from TSR Mobile

Reply 52

subject1

18

Original post by Saywhatyoumean

How do you find the maximum number of interchanges needed to sort a list if six pieces of data using bubble sort??

Posted from TSR Mobile

well its 5 isnt it, cos if its completely the other way round, then u just swap them all to the end.

Reply 53

Saywhatyoumean

10

Original post by subject1

well its 5 isnt it, cos if its completely the other way round, then u just swap them all to the end.

Oh the textbook says 15

I think its because you can have (copied from yahoo answers)

(6 5 4 3 2 1) [initial list]

(5 6 4 3 2 1)
(5 4 6 3 2 1)
(5 4 3 6 2 1)
(5 4 3 2 6 1)
(5 4 3 2 1 6)

(4 5 3 2 1 6)
(4 3 5 2 1 6)
(4 3 2 5 1 6)
(4 3 2 1 5 6)

(3 4 2 1 5 6)
(3 2 4 1 5 6)
(3 2 1 4 5 6)

(2 3 1 4 5 6)
(2 1 3 4 5 6)

(1 2 3 4 5 6)

Reply 54

bigboateng

3

Original post by Saywhatyoumean

Oh the textbook says 15

I think its because you can have (copied from yahoo answers)

(6 5 4 3 2 1) [initial list]

(5 6 4 3 2 1)
(5 4 6 3 2 1)
(5 4 3 6 2 1)
(5 4 3 2 6 1)
(5 4 3 2 1 6)

(4 5 3 2 1 6)
(4 3 5 2 1 6)
(4 3 2 5 1 6)
(4 3 2 1 5 6)

(3 4 2 1 5 6)
(3 2 4 1 5 6)
(3 2 1 4 5 6)

(2 3 1 4 5 6)
(2 1 3 4 5 6)

(1 2 3 4 5 6)

Formula is 1/2(n)(n-1)

Posted from TSR Mobile

Reply 55

bigboateng

3

Original post by Saywhatyoumean

How do you find the maximum number of interchanges needed to sort a list if six pieces of data using bubble sort??

Posted from TSR Mobile

1/2n(n-1)

Posted from TSR Mobile

Reply 56

subject1

18

Original post by Saywhatyoumean

Oh the textbook says 15

I think its because you can have (copied from yahoo answers)

(6 5 4 3 2 1) [initial list]

(5 6 4 3 2 1)
(5 4 6 3 2 1)
(5 4 3 6 2 1)
(5 4 3 2 6 1)
(5 4 3 2 1 6)

(4 5 3 2 1 6)
(4 3 5 2 1 6)
(4 3 2 5 1 6)
(4 3 2 1 5 6)

(3 4 2 1 5 6)
(3 2 4 1 5 6)
(3 2 1 4 5 6)

(2 3 1 4 5 6)
(2 1 3 4 5 6)

(1 2 3 4 5 6)

no i meant 5 sorts