Mathematics: Post your doubts here!

Saad the Paki · May 8, 2015

loaie Amgad said:
guys what was the answer for recurring question????

23/90

misscute406 · May 8, 2015

guys need your help!! 0500/04/sp/2014 Question 4a)(i)
I always have a problem solving these kind of questions!! Kindly tell me the method to solve these questions!!

The diagram shows a plastic cup in the shape of a cone with the end removed.
The vertical height of the cone in the diagram is 20 cm.
The height of the cup is 8 cm.
The base of the cup has radius 2.7 cm. (a) (i) Show that the radius, r, of the circular top of the cup is 4.5 cm.

Suhayb.B · May 8, 2015

misscute406 said:
guys need your help!! 0500/04/sp/2014 Question 4a)(i)
I always have a problem solving these kind of questions!! Kindly tell me the method to solve these questions!!

The diagram shows a plastic cup in the shape of a cone with the end removed.
The vertical height of the cone in the diagram is 20 cm.
The height of the cup is 8 cm.
The base of the cup has radius 2.7 cm. (a) (i) Show that the radius, r, of the circular top of the cup is 4.5 cm.

The 2 triangles are similar. I'll give you a hint; find the scale factor (LSF) of both triangles. The radius of the circular top will be the LSF * 2.7.

http://www.cie.org.uk/images/147813-2015-paper-4-specimen-paper.pdf

misscute406 · May 8, 2015

Suhayb.B said:
The 2 triangles are similar. I'll give you a hint; find the scale factor (LSF) of both triangles. The radius of the circular top will be the LSF * 2.7.

http://www.cie.org.uk/images/147813-2015-paper-4-specimen-paper.pdf

How to find?? I didn't get you!!

misscute406 · May 8, 2015

Why should we find curved surface area of both the cones and then subtract for question 4b)(ii) 0580/04/SP/15

(ii) Calculate the curved surface area of the outside of the cup.
[The curved surface area, A, of a cone with radius r and slant height l is A = πrl.]

Suhayb.B · May 8, 2015

misscute406 said:
How to find?? I didn't get you!!

Okay.
If you look at the figure, you will see 2 triangles (the inner triangle and the outer triangle). The outer triangle is an enlargement of the inner triangle. The outer triangle's height is 20 cm, while the inner triangle's height is 20 - 8 = 12 cm. The scale factor is then 20/12 = 5/3. This means that outer triangle's height is (5/3) of the inner. Similarly, the outer radius is an enlargement of the inner radius and hence is 5/3 of the inner. Therefore, the radius of the top is (5/3 * 2.7) = 4.5

IF you still don't understand (as my explanation may be hard to understand), see this: http://www.bbc.co.uk/schools/gcsebitesize/maths/geometry/congruencysimilarityrev1.shtml and
http://www.bbc.co.uk/schools/gcsebitesize/maths/geometry/congruencysimilarityrev4.shtm

misscute406 · May 8, 2015

Suhayb.B said:
Okay.
If you look at the figure, you will see 2 triangles (the inner triangle and the outer triangle). The outer triangle is an enlargement of the inner triangle. The outer triangle's height is 20 cm, while the inner triangle's height is 20 - 8 = 12 cm. The scale factor is then 20/12 = 5/3. This means that outer triangle's height is (5/3) of the inner. Similarly, the outer radius is an enlargement of the inner radius and hence is 5/3 of the inner. Therefore, the radius of the top is (5/3 * 2.7) = 4.5

IF you still don't understand (as my explanation may be hard to understand), see this: http://www.bbc.co.uk/schools/gcsebitesize/maths/geometry/congruencysimilarityrev1.shtml and
http://www.bbc.co.uk/schools/gcsebitesize/maths/geometry/congruencysimilarityrev4.shtm

Thank you!! I understood!!

misscute406 · May 8, 2015

Suhayb.B said:
Okay.
If you look at the figure, you will see 2 triangles (the inner triangle and the outer triangle). The outer triangle is an enlargement of the inner triangle. The outer triangle's height is 20 cm, while the inner triangle's height is 20 - 8 = 12 cm. The scale factor is then 20/12 = 5/3. This means that outer triangle's height is (5/3) of the inner. Similarly, the outer radius is an enlargement of the inner radius and hence is 5/3 of the inner. Therefore, the radius of the top is (5/3 * 2.7) = 4.5

IF you still don't understand (as my explanation may be hard to understand), see this: http://www.bbc.co.uk/schools/gcsebitesize/maths/geometry/congruencysimilarityrev1.shtml and
http://www.bbc.co.uk/schools/gcsebitesize/maths/geometry/congruencysimilarityrev4.shtm

Explain this too!!

Why should we find curved surface area of both the cones and then subtract for question 4b)(ii) 0580/04/SP/15

(ii) Calculate the curved surface area of the outside of the cup.
[The curved surface area, A, of a cone with radius r and slant height l is A = πrl.]

Suhayb.B · May 8, 2015

misscute406 said:
Explain this too!!

Why should we find curved surface area of both the cones and then subtract for question 4b)(ii) 0580/04/SP/15

(ii) Calculate the curved surface area of the outside of the cup.
[The curved surface area, A, of a cone with radius r and slant height l is A = πrl.]

No problem.. The plastic cup is the shaded part of the cone. It is the result of removing a section of the cone, giving the frustum shape, and leaving another cone. So the cup is really just the difference of the 2 cones. You subtract the smaller cone from the bigger cone to get the cup. Therefore the curved surface area for the cup is the difference between both curved surface areas.
I hope that clears it?

misscute406 · May 8, 2015

Ooh Okay!! Thnak you soo much for the explanation!!

NOneed2speedd · May 8, 2015

Hello...need help in these questions:
1) Q.11 part d (i) and d (ii)

NOneed2speedd · May 8, 2015

And in Q.4 last part i can't understand ... we use formula vol.discharge:crossarea×speed×time
but when i use pie(0.5)^2 i get ans. Wrong and when i only do 33000/1800 i get right ans.. why is that

S.sarraf · May 9, 2015

Heyy does anyone have maths paper 4 2015 of March series ? My exam is tmmr and I need it badly . Thank you in advance . You. Can mail me on [email protected] . May god bless you .

S.sarraf · May 9, 2015

Heyy does anyone have maths paper 4 2015 of March series ? My exam is tmmr and I need it badly . Thank you in advance . You. Can mail me on [email protected] . May god bless you .

misscute406 · May 9, 2015

NOneed2speedd said:
Hello...need help in these questions:
1) Q.11 part d (i) and d (ii)

which year is that??

misscute406 · May 9, 2015

NOneed2speedd said:
Hello...need help in these questions:
1) Q.11 part d (i) and d (ii)

Hope you understand:
https://fbcdn-sphotos-c-a.akamaihd...._=1439803102_8352f7c555435a5cc9452168318eda61

I am sorry about the part (ii)

misscute406 · May 9, 2015

I have only the worked out paper!! All the best!!

S.sarraf said:
Heyy does anyone have maths paper 4 2015 of March series ? My exam is tmmr and I need it badly . Thank you in advance . You. Can mail me on [email protected] . May god bless you .

misscute406 · May 9, 2015

NOneed2speedd said:
And in Q.4 last part i can't understand ... we use formula vol.discharge:crossarea×speed×time
but when i use pie(0.5)^2 i get ans. Wrong and when i only do 33000/1800 i get right ans.. why is that

was it helpful??

NOneed2speedd · May 9, 2015

misscute406 said:
Hope you understand:
https://fbcdn-sphotos-c-a.akamaihd...._=1439803102_8352f7c555435a5cc9452168318eda61

I am sorry about the part (ii)

Oh thank u vert much

misscute406 · May 9, 2015

NOneed2speedd said:
Oh thank u vert much

My Pleasure!!

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Mathematics: Post your doubts here!

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