I'm an IGCSE Maths Teacher - Post your questions here.

[AlphaWolf]

In q1(B), why do we multiply the multiplier and not divide, which we normally do. I really don't understand this.
http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Mathematics (0580)/0580_w10_qp_42.pdf

 

[notnek01]

In q1(B), why do we multiply the multiplier and not divide, which we normally do. I really don't understand this.
http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Mathematics (0580)/0580_w10_qp_42.pdf

i) or ii)?

And can you explain your question in detail?

 

[AlphaWolf]

how do u find the slant height of a cone?

 

[AlphaWolf]

b(I). Normally when performing reverse percentages, we divide by the multiplier. however in tis case we had to multiply.

 

[notnek01]

how do u find the slant height of a cone?

Sometimes it is given to you.

If you only know the radius and the perpendicular height, you can use Pythagoras to find the hypotenuse which is the slant height.

 

[notnek01]

b(I). Normally when performing reverse percentages, we divide by the multiplier. however in tis case we had to multiply.

This is not reverse percentages.

The question asks you to increase 7800 by 15%.

If the question gave you the earnings in 2009 and asked you to find the earnings in 2008, you would need to use reverse percentages methods.

 

[shazmina]

http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Mathematics (0580)/0580_w11_qp_43.pdf could u plzzz let me knw how to solve de question 12 part (b) 3.....of dis paper ie about sequence...

 

[notnek01]

http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Mathematics (0580)/0580_w11_qp_43.pdf could u plzzz let me knw how to solve de question 12 part (b) 3.....of dis paper ie about sequence...

I answered this in post #414 in this thread.

 

[TheJDOG]

http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Mathematics (0580)/0580_s12_qp_42.pdf

11)b , can you plz do it for me?

 

[inquisitiveness]

oh okay thanks,this is a similar question http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Mathematics (0580)/0580_w10_qp_41.pdf but only last d is the problem,what i did was 4-1 = 1/2 x 2 (2+1)
3=3
but the answer is for 3 marks so thats it or do i have to shwo them in a different way

 

[notnek01]

http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Mathematics (0580)/0580_s12_qp_42.pdf

11)b , can you plz do it for me?

The shaded area is made up of a sector and a rectangle.

Sector: Area = pi(12^2)*(22/360)=8.8 pi

The width of the rectangle is the arc length of the sector so first we need the arc length:

Arc length = 2*pi*12*22/360 = (22/15) pi

Rectangle: Area = 7* (22/15) pi = (154/15) pi


Shaded area = 8.8 pi + (154/15) pi = 59.9 cm^2

 

[notnek01]

oh okay thanks,this is a similar question http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Mathematics (0580)/0580_w10_qp_41.pdf but only last d is the problem,what i did was 4-1 = 1/2 x 2 (2+1)
3=3
but the answer is for 3 marks so thats it or do i have to shwo them in a different way

Which question?

 

[inquisitiveness]

http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Mathematics (0580)/0580_w08_ms_4.pdf q/10 b i)please if you dont mind
I did 2(1+2+3+4....)=2n(2n+1)/2 and simplified to get n(2n+1) not n (n+1):/

 

[inquisitiveness]

l

Which question?

last question Q.9 D

 

[TheJDOG]

Thanks a lot! I understand now.

 

[notnek01]

http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Mathematics (0580)/0580_w08_ms_4.pdf q/10 b i)please if you dont mind
I did 2(1+2+3+4....)=2n(2n+1)/2 and simplified to get n(2n+1) not n (n+1):/

2(1+2+3+4+5...+n) = 2[n(n+1)/2] = n(n+1)

I don't know why you multiplied the n in brackets by 2. Maybe you're getting confused with function methods e.g. f(2n). But here we need 2f and not f(2n).

 

[notnek01]

oh okay thanks,this is a similar question http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Mathematics (0580)/0580_w10_qp_41.pdf but only last d is the problem,what i did was 4-1 = 1/2 x 2 (2+1)
3=3
but the answer is for 3 marks so thats it or do i have to shwo them in a different way

You have shown that S_2 - S_1 = P_1.

But you haven't shown that S_n - S_(n-1) = P_n works for all n.

You need to use algebra with S_n = 1/6 n (n+1)(n+2)

 

[inquisitiveness]

OooO ok for the next step of http://papers.xtremepapers.com/CIE/Cambridge%20IGCSE/Mathematics%20(0580)/0580_w08_qp_4.pdf q.10 b ii i did 100(100+1) but its wrong idk how im supposed to think !!

 

[AlphaWolf]

Thx a billion, I understand now!

 

[inquisitiveness]

You have shown that S_2 - S_1 = P_1.

But you haven't shown that S_n - S_(n-1) = P_n works for all n.

You need to use algebra with S_n = 1/6 n (n+1)(n+2)

oh okay so i attached my working of the sn thing so far but idk how to continue