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OCR Maths A - How did people find it ?

overall that test was easy, the only question i did not understand was the 2 way table but i made an educated guess.

Also stupidly i mucked up on the obtuse angle parlleogram, because i did not read the question properly and did not use the cosine rule, which i can use perfectly. Oh well 95% aint bad.

Reply 41

Katermerang

1

oh no it was £180 almost .........

Reply 42

Katermerang

1

yeah the gradient of the line was £24 for every hour plus 60

24*5= 120 120+60=180

Reply 43

Katermerang

1

yeah sure dont worry too much its over now.

Reply 44

Haruhi

The answer for the final question was 374.477 :smile:

its the volume of the bigger cone minus volume of smaller cone. The total height of the big cone was 14.4 :smile:

YES 14.4! I even asked my teacher so dont dare to oppose! XD

O-O 8^p = (2^3)^p
for the second question about that i got wrong -__-;

WTF TABLE? and parallelogram! O-O I FAILED!

I got complete the square wrong as well T__T my eyes started to play on me T__T not fair...

the angle one where you had to find x in that star thing i got wrong T__T

CARELESS MISTAKES DAMN IT! T^T

£C = 60 + 24 x h right?!

Reply 45

milliondollarcorpse

16

Haruhi

£C = 60 + 24 x h right?!

yep

Reply 46

Katermerang

1

the cone height was 15 i explained in detail why a few posts a go, trust me its 15 14.4 does not work.

Reply 47

milliondollarcorpse

16

14.4!
I put that so it must be right :p:

Reply 48

Katermerang

1

milliondollarcorpse

14.4!
I put that so it must be right :p:

no look your scale factor is 2.4 yeah

so height of cone= 14.4

14.4/2.4 = 6 not 5 which is the cone radius

my scale factor it works. sc=3
15/3= 5 = radius of cone

understand?

Reply 49

Haruhi

5/5 = 1 (radius of smaller cone)
So scale factor is 5

12/5 = 2.4 (height of smaller cone)

2.4 + 12 = 14.4 (height of bigger cone)

14.4 is CORRECT O-O!

cheer up people, even if you loose 20 marks on each paper you will still end up with 80% over all which is a A or A*

Reply 50

toby_ling

Don't forget the radii for the frustum and the original cone would have had to be the same:

Radius of frustum: 5 cm
Radius of original, large cone: 5 cm
Radius of small cone: 1 cm

Height of frustum: 12 cm

That being said, the ratios of the frustum and the small cone should have been (in my view) as follows:

Radius Ratio (on which other calculations would have been based on):

Frustum :s-smilie:

mall Cone
5:1

(1/5)

So, height of the small cone would also have been in the same ration:

Frustum: Small Cone
12:??

...and so the height (t) of the small cone...

t/12 = 1/5
--> t = 2.4

When added to the height of the frustum, this would have given the height of the original cone as (12+2.4) 14.4 cm.

Open to corrections. :smile:

Reply 51

Haruhi

Katermerang

no look your scale factor is 2.4 yeah

so height of cone= 14.4

14.4/2.4 = 6 not 5 which is the cone radius

my scale factor it works. sc=3
15/3= 5 = radius of cone

understand?

scale factor is not 2.4, its 5!

Yea! 14.4!

Go 14.4!! lol

no i see perfectly what your doing to get 14.4 but is wrong. look this question works on simar trangles draw a line from the centre base of the small cone (trinagle cross section) to the large cone centre do you even get a tryangle no you get a quailateral how can a quad and a tryangle be similar?

Reply 55

toby_ling

Erm, I'm very sorry but I don't quite understand what you are trying to say. Perhaps you could phrase your explanation again? It certainly has merit and I would like to understand it completely.

Thank You.

Reply 56

AnonyMatt

15

I can see why it is 15, though I put 14.4.
Stop being so stubborn people.
Maths teachers are always wrong.
You'll only have lost 2 marks anyway.
One mark for being totally wrong, fools (I did it aswell, so I can make fun of you, it's the law) and 1 mark for obviously getting the wrong answer.
You get 1 mark for writing down the correct formula anyway.
Another mark for substituting the correct values into it, according to your initial workings.
Another mark for working out the formula correctly.

Reply 57

Katermerang

1

toby_ling

Erm, I'm very sorry but I don't quite understand what you are trying to say. Perhaps you could phrase your explanation again? It certainly has merit and I would like to understand it completely.

Thank You.

of course if i knew how to import pictures it would make this so much easier ok do this:

1. imagine a line from the centre of the the base of the first cone, right down to the centre of the base of the large cone
2. cut a trinagle cross section in you head
3. is this shape (the one made from the line inside the fustrum) a tryangle, no, so how can this be similar to to the cross section of the other smaller cone.

4. now imagine a line from the end of the base of the first cone perpindicular to the base is this a trinagle? yes, is this similar? yes and what size is its base 4cm (5-1) 1+radius of smaller tyangle.

5. now find the scale factor 12/4 =3
6. 3*1 =3 3+12=15
7 we know the scale factor is 3 so take a cross section of the whole cone 15/3 = 5 which what a conisidence just happens to be the size of the base.

8. if we use 2.4 as our scale factor with our height as 14.4 (12/5 =2.4)
and use this as the sc 15/2.4 = 6 not 5 so it cant be 14.4

thats the best i can do without a diagram.

Reply 58

Katermerang

1

AnonyMatt

I can see why it is 15, though I put 14.4.
Stop being so stubborn people.
Maths teachers are always wrong.
You'll only have lost 2 marks anyway.
One mark for being totally wrong, fools (I did it aswell, so I can make fun of you, it's the law) and 1 mark for obviously getting the wrong answer.
You get 1 mark for writing down the correct formula anyway.
Another mark for substituting the correct values into it, according to your initial workings.
Another mark for working out the formula correctly.

my greatest gratitiude i was starting to go crazy.

Reply 59

toby_ling

Katermerang

of course if i knew how to import pictures it would make this so much easier ok do this:

1. imagine a line from the centre of the the base of the first cone, right down to the centre of the base of the large cone
2. cut a trinagle cross section in you head
3. is this shape (the one made from the line inside the fustrum) a tryangle, no, so how can this be similar to to the cross section of the other smaller cone.

4. now imagine a line from the end of the base of the first cone perpindicular to the base is this a trinagle? yes, is this similar? yes and what size is its base 4cm (5-1) 1+radius of smaller tyangle.

5. now find the scale factor 12/4 =3
6. 3*1 =3 3+12=15
7 we know the scale factor is 3 so take a cross section of the whole cone 15/3 = 5 which what a conisidence just happens to be the size of the base.

8. if we use 2.4 as our scale factor with our height as 14.4 (12/5 =2.4)
and use this as the sc 15/2.4 = 6 not 5 so it cant be 14.4

thats the best i can do without a diagram.

Thank you for the exegesis. However, I shall stick to my view for now. :biggrin:

We'll see who was right when the answers are released.

OCR Maths A - How did people find it ?

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