Do not understand the wording of this circles question...

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#1
Q: http://prntscr.com/vs5g3k

What does the "diameter of the centre" even mean? Are all the shaded sectors part of a sector from the same circle?. Here is how I interpreted it: http://prntscr.com/vs5ig9
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1 month ago
#2
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1 month ago
#3
I agree with OP's interpretation.
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#4
(Original post by Justvisited)
How?
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1 month ago
#5
The (part of) sector radius is 1.8, not 2.2.
Apart from that, it looks ok.
Last edited by mqb2766; 1 month ago
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1 month ago
#6
(Original post by TSR360)
How?
as the grey shaded sector doesn't go all the way to the edge of the broach it cant have a radius of 2.2 even if you extend it to the mid point like you have. otherwise, the diameter of the whole broach would have to be more that 4.4 which it cant (as stated in the question).

I believe the length you have labelled as 2.2 should be 1.8
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1 month ago
#7
(Original post by TSR360)
Q: http://prntscr.com/vs5g3k

What does the "diameter of the centre" even mean? Are all the shaded sectors part of a sector from the same circle?. Here is how I interpreted it: http://prntscr.com/vs5ig9
the centre is circular therefore it has a diameter
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#8
(Original post by the bear)
the centre is circular therefore it has a diameter
Here's my w/o: http://prntscr.com/vs742i

What did I do wrong? If it's in radians, do I keep the RAD mode on in my calculator even if I'm not dealing with angles? I tried that but I still get the wrong answer http://prntscr.com/vs7ft7
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1 month ago
#9
(Original post by TSR360)
Here's my w/o: http://prntscr.com/vs742i

What did I do wrong? If it's in radians, do I keep the RAD mode on in my calculator even if I'm not dealing with angles? I tried that but I still get the wrong answer http://prntscr.com/vs7ft7
What is c2? Radius seems way too large?
If you add the 4 sectors together you get a (part of) semi circle. Can't see why you'd particularly use radians.
Last edited by mqb2766; 1 month ago
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1 month ago
#10
Area of big circle = 𝝅 x 2.22

the shaded bits can be joined up to make a semicircle with a small semicircle removed:

grey semicircle area = 𝝅 x 1.82/2

small semicircle area = 𝝅 x 0.52/2

area of shaded bits = 𝝅 x 1.82/2 - 𝝅 x 0.52/2

Area of metal = Area of big circle - area of shaded bits....

once you know the area of metal you can then find its volume.
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#11
(Original post by mqb2766)
What is c2? Radius seems way too large?
If you add the 4 sectors together you get a (part of) semi circle. Can't see why you'd particularly use radians.
c2 is the circle around the 4 shaded segments. I can only get the right answer if I leave RAD mode on and do all my calculations with radians, why is that?
Last edited by TSR360; 1 month ago
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1 month ago
#12
(Original post by TSR360)
c2 is the circle around the 4 shaded segments. I can only get the right answer if I leave RAD mode on and do all my calculations with radians, why is that?
I don't know what calcs you've done, but using radians is unnecessary. Upload with a bit extra explanation of you want some feedback.
See the bears post for simply adding/subtracting 3 circles and semi circles.It's the easiest way.
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