Mathematics: Post your doubts here!

[notnek01]

shouldn't the answer be 2/12 for Question 21a in this paper?

http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Mathematics (0580)/0580_s12_qp_21.pdf

No it should be 1/12. Can you explain why you think it's 2/12?

 

[weirdoatlarge77]

Please explain question 10a and b pleasee!
http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Mathematics (0580)/0580_s10_qp_22.pdf

 

[weirdoatlarge77]

No it should be 1/12. Can you explain why you think it's 2/12?

I thought 'cause there are two ways of getting two Reds, (3/9 x 2/8) + (3/9 x 2/8) ?

 

[notnek01]

I thought 'cause there are two ways of getting two Reds, (3/9 x 2/8) + (3/9 x 2/8) ?

There's only one way of getting two red pencils: a red pencil on the first choice and a red pencil on the second choice.

 

[notnek01]

Please explain question 10a and b pleasee!
http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Mathematics (0580)/0580_s10_qp_22.pdf

Are you sure you mean Q10? This is an algebra question with no parts (a) and (b).

 

[weirdoatlarge77]

I thought 'cause there are two ways of getting two Reds, (3/9 x 2/8) + (3/9 x 2/8) ?

Oh ok.
Could you explain this?
Question 10a and b pleasee
http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Mathematics (0580)/0580_s10_qp_22.pdf

 

[weirdoatlarge77]

so

Oh ok.
Could you explain this?
Question 10a and b pleasee
http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Mathematics (0580)/0580_s10_qp_22.pdf

Sorry (what's wrong with me?)
Question 8a &b

 

[notnek01]

so

Sorry (what's wrong with me?)
Question 8a &b

This question keeps being asked. Here's one of the times I answered it: https://www.xtremepapers.com/commun...maths-teacher-post-your-questions-here.24660/

(Post #13).

 

[A star]

so

Sorry (what's wrong with me?)
Question 8a &b

for first part just find the point of intersection
second part just draw the graph0.5cosx and find points of intersection whats soo difficult i dont get

 

[notnek01]

for first part just find the point of intersection
second part just draw the graph0.5cosx and find points of intersection whats soo difficult i dont get

Do you mean draw the graph of '0.5 + cosx' ? A 0.5 cos(x) graph won't help here.

Your method would work but it would waste time plus you'd need to draw the graph accurately.

The best method is to estimate where the difference between the curves is 0.5.

 

[A star]

Do you mean draw the graph of '0.5 + cosx' ? A 0.5 cos(x) graph won't help here.

Your method would work but it would waste time plus you'd need to draw the graph accurately.

The best method is to estimate where the difference between the curves is 0.5.

yeah it is time consuming but at that time in the paper you do that method which clicks as you dont have time to search for easier one (though u r rite) . it was a typo

 

[notnek01]

yeah it is time consuming but at that time in the paper you do that method which clicks as you dont have time to search for easier one (though u r rite) . it was a typo

It seems like a risky method since the question says, 'Use the graph to solve the equations'.

So by drawing another graph, you're not really doing what is asked. You wouldn't lose a mark here for not following instructions but may in another question.

 

[james1234]

http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Mathematics (0580)/0580_w12_qp_21.pdf question 13, do we just multiply the matrix of x and y=x?

 

[notnek01]

http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Mathematics (0580)/0580_w12_qp_21.pdf question 13, do we just multiply the matrix of x and y=x?

Two ways to do this question:

You could find the matrices of the two transformations and then multiply the two matrices with the y=x matrix on the left.

Or you could use the unit vector method. Transform the unit vectors (1,0) and (0,1) by the two transformations and write the results as the columns of a matrix.

If you've learnt the transformation matrices then the first method is probably better. If you haven't then I'd go with the second method.

 

[james1234]

Two ways to do this question:

You could find the matrices of the two transformations and then multiply the two matrices with the y=x matrix on the left.

Or you could use the unit vector method. Transform the unit vectors (1,0) and (0,1) by the two transformations and write the results as the columns of a matrix.

If you've learnt the transformation matrices then the first method is probably better. If you haven't then I'd go with the second method.

Got it, thanks a lot

 

[Princess Raven]

If we substitute 800 it will give us the answer to

1 + 2 + 3 + ... + 798 + 799 + 800

Then if we divide this sum by 2 we get:

1/2 (1 + 2 + 3 + ... + 798 + 799 + 800) = 0.5 + 1 + 1.5 + ... + 399.5 + 400

But this is not what the question is asking for.


Instead, if we substitute 400 into the formula and multiply by 2 we have:

2(1 + 2 + 3 + ... + 398 + 399 + 400) = 2 + 4 + 6 + ... + 796 + 798 + 800


Does this make sense?

OMG THANK U LIKE SOOO MUCH!!!! i hate these stupid sequence question!! so this is the method we always use right?? but u know sometimes they give us the formula for n like in this case and they go like now find the formula for 2n??? or 2n-1? how in the world r we suppose to do that? do u know a method?

 

[sj0007]

OMG THANK U LIKE SOOO MUCH!!!! i hate these stupid sequence question!! so this is the method we always use right?? but u know sometimes they give us the formula for n like in this case and they go like now find the formula for 2n??? or 2n-1? how in the world r we suppose to do that? do u know a method?

substitute 2n or 2n-1 in the place of n....

 

[qusaifares10]

can you tell me any casio calculator that i can use for the exam?

 

[notnek01]

can you tell me any casio calculator that i can use for the exam?

You can use any Casio Scientific Calculator

e.g.

FX-50
FX-991
FX-83
FX-85
FX-115

 

[Princess Raven]

substitute 2n or 2n-1 in the place of n....

SO Whereever in the formula we see an n we just make that 2n or 2n-1?