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Incredibly hard GCSE question

Please take a look, I cannot get my head around it whatsoever. I would really appreciate someone to explain to me how to tackle it. Thanks :smile:
Incredibly hard question.pdf49.1KB
63° I think. I worked out the circumference of the cone relative to the circumference of the would be full circle.
Reply 2
Avatar for TheJ0ker
TheJ0ker
11
Original post by recurring500
Please take a look, I cannot get my head around it whatsoever. I would really appreciate someone to explain to me how to tackle it. Thanks :smile:


You need to know s=Rθs=R\theta where s is arc length and the angle (theta) is measured in radians.

So from the cross section diagram you can see the diameter of the circular top of the cone is 4.9 so circumference is 4.9π4.9\pi can you see what to do now?
Reply 3
Avatar for BabyMaths
BabyMaths
Original post by TheJ0ker
You need to know s=Rθs=R\theta where s is arc length and the angle (theta) is measured in radians.

So from the cross section diagram you can see the diameter of the circular top of the cone is 4.9 so circumference is 4.9π4.9\pi can you see what to do now?


Thread title refers to GCSE so we should quote arc length = θ360×π×d\frac{\theta}{360}\times \pi \times d rather than s=rθs=r\theta
You don't need radian measure at all.

Circumference of top of cone = pi x diameter = 4.9 pi

This equals the length of the arc (ignoring the bit that would overlap so it could be glued).

Using the standard GCSE formula, arc length = angle /360 x 2 x 14 x pi

So angle = 4.9 x 360 / 28 = 63
Lol, negged for getting the question right... Now i've seen everything haha
Reply 6
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TheJ0ker
11
Original post by BabyMaths
Thread title refers to GCSE so we should quote arc length = θ360×π×d\frac{\theta}{360}\times \pi \times d rather than s=rθs=r\theta


Do you get that formula at GCSE or do you have to remember it?
Reply 7
Avatar for BabyMaths
BabyMaths
No you don't get it.

You should remember the formulae for the area and circumference of a circle.

Arc length is the fraction angle360\frac{angle}{360} of the circumference and sector area is the fraction angle360\frac{angle}{360} of the area of the circle.
Reply 8
Avatar for recurring500
recurring500
OP
11
Thanks everyone, got it now! It's much easier than I thought, perhaps a rather exaggerated title. Everyone got a positive rating as you all really helped, thanks.
Original post by Mr M
You don't need radian measure at all.

Circumference of top of cone = pi x diameter = 4.9 pi

This equals the length of the arc (ignoring the bit that would overlap so it could be glued).

Using the standard GCSE formula, arc length = angle /360 x 2 x 14 x pi

So angle = 4.9 x 360 / 28 = 63


Unless I'm missing the obvious, with that, don't you end up with:

(x) = Multiplied
63 = Pi (x) x


Shouldn't you divide by X? I think I've missed the obvious.
Original post by ThatPerson
Unless I'm missing the obvious, with that, don't you end up with:

(x) = Multiplied
63 = Pi (x) x


Shouldn't you divide by X? I think I've missed the obvious.


Yes you have done something wrong. I'm not sure what.
Original post by Mr M
Yes you have done something wrong. I'm not sure what.


Ah, I meant divide by Pi.

I think I'm even more confused now :smile:

Surely if you have:

Arc length = \frac{x}{360} \pi D

It would rearrange to:

176428π=x \frac{1764} {28\pi} = x


If you add in the values?

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