Mathematics: Post your doubts here!

[Shada Mohammed]

Divide 84.5 by 3, you get 28.167 = 28.2 cm
Divide 85.5 by 3, you get 28.500 = 28.5 cm

How are you getting 28.7 and 28.8?

Well I tlhought of dividing 85 first by 3 then I got the limits I am not convinced that I should directly divide it by 3 after getting the limits of perimeter

 

[Phoenix Blood]

Well I tlhought of dividing 85 first by 3 then I got the limits I am not convinced that I should directly divide it by 3 after getting the limits of perimeter

You already got the upper and lower bound for the entire perimeter, you needn't meddle with each side now, and just simple divide it by three.

Using your method : 85/3 = 28.3333. The upper and lower limits still don't account to 28.7 and 28.8 if you work out with them.

 

[Shada Mohammed]

The answer in the book is 1/3(a+b) I don't know how to work it out

 

[Phoenix Blood]

The answer in the book is 1/3(a+b) I don't know how to work it out

cross multiply

 

[Shada Mohammed]

http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Mathematics (0580)/0580_s07_qp_4.pdf
question 9 part c (ii) why we have to equalise the equation with 14 I thought of equalising it with 12 instead of 14.

 

[Faiza Anwar]

how to solve question 18 m/j 2014 p22 plzz help!!

 

[Faiza Anwar]

http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Mathematics (0580)/0580_s07_qp_4.pdf
question 9 part c (ii) why we have to equalise the equation with 14 I thought of equalising it with 12 instead of 14.

you can multiply eq 1 by 2 or 4 if u wish....

 

[Phoenix Blood]

how to solve question 18 m/j 2014 p22 plzz help!!View attachment 48349

OMG this question had come in our exams and i loved it

See, throughout, we apply the principle that Volume = Area * length ( whatever length of cross-section... ), and step-by-step, we find each of the variables for both the containers.

For the large container, we have the volume and area, so let's find its length-
Volume = area * length
3456 = 1024 * length
length = 3.375 cm

For the smaller container, we will first find its length in order to get its area, by comparing its values with the bigger shape as they both are similar.
Using the formula V1/v2 = (length1/length2)^3, we substitute (the formula is somewhat that, i don't know how you write it)
3456/1458 = (3.375/length2)^3
length2 = 2.53125 (don't cut off decimal numbers even after three decimal places. Use the calculator to work out the answer)

Now you have the length as well as the volume for the smaller container,
Volume = area * length
1458 = area * 2.53125
area = 576

Erm... i hope you got it :/

 

[Shada Mohammed]

Find the value of w when X^75 ÷X^w = x^8

 

[Phoenix Blood]

Find the value of w when X^75 ÷X^w = x^8

Make w the subject of the formula?

 

[Thought blocker]

A box contains 3 red pencils, 2 blue pencils and 4 green pencils.
Raj chooses 2 pencils at random, without replacement.

Calculate the probability that: Exactly one for the two chosen pencils is green.
Thought blocker

There are 9 pencils, so there are 9C2 = 9x8/2 = 36 ways to pick 2 pencils.
To get exactly 1 green pencil, there is 1 green and 1 other.
Raj picks from 4 green and 5 others.
There are 4 ways to pick one green and 5 ways to pick the other.
4x5 = 20 ways to pick exactly 1 green
20/36 = 5/9

 

[snowbrood]

Find the value of w when X^75 ÷X^w = x^8

(x^75)/(x^8)=x^w
x^(75-8)=x^w
w=(75-8)=67

 

[Sariya Khan]

There are 9 pencils, so there are 9C2 = 9x8/2 = 36 ways to pick 2 pencils.
To get exactly 1 green pencil, there is 1 green and 1 other.
Raj picks from 4 green and 5 others.
There are 4 ways to pick one green and 5 ways to pick the other.
4x5 = 20 ways to pick exactly 1 green
20/36 = 5/9

Thanks a ton

 

[Thought blocker]

Thanks a ton

You're welcome.

 

[<--h-->]

can anyone please help me with this question?...part b

 

[idklol]

How much do the examiners care about working out?
There's hella funky stuff in paper 2 in terms of working.
Would you get away with just showing what you did in your calculator and getting the answer correct?

 

[drboron]

OMG this question had come in our exams and i loved it

See, throughout, we apply the principle that Volume = Area * length ( whatever length of cross-section... ), and step-by-step, we find each of the variables for both the containers.

For the large container, we have the volume and area, so let's find its length-
Volume = area * length
3456 = 1024 * length
length = 3.375 cm

For the smaller container, we will first find its length in order to get its area, by comparing its values with the bigger shape as they both are similar.
Using the formula V1/v2 = (length1/length2)^3, we substitute (the formula is somewhat that, i don't know how you write it)
3456/1458 = (3.375/length2)^3
length2 = 2.53125 (don't cut off decimal numbers even after three decimal places. Use the calculator to work out the answer)

Now you have the length as well as the volume for the smaller container,
Volume = area * length
1458 = area * 2.53125
area = 576

Erm... i hope you got it :/

That would probably get you a right answer wrong working mark. The correct method is to calculate the volume scale factor (k^3) and use that to find the area scale factor (k^2)

k^3 = 1458/3456
k^3 = 27/64
k = 3/4
k^2 = 9/16

Hence the surface area of the smaller shape is
A = 1024*9/16 = 576cm^2

 

[Shada Mohammed]

Make w the subject of the formula?

No it says to find the value of w I did it and the answer which I got was 67 while the answer in the markschene is 64

 

[Shada Mohammed]

There are 9 pencils, so there are 9C2 = 9x8/2 = 36 ways to pick 2 pencils.
To get exactly 1 green pencil, there is 1 green and 1 other.
Raj picks from 4 green and 5 others.
There are 4 ways to pick one green and 5 ways to pick the other.
4x5 = 20 ways to pick exactly 1 green
20/36 = 5/9

What is 9c2?

 

[Thought blocker]

What is 9c2?

9combination2