A Level Product Design Maths Question help

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Anonymous_4657
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I'm stuck on this question. For the cylinder on the top I got the volume to be 6^2 π x 72. It this correct? The mark scheme says it is 36^2 π x 12.
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qwertyuiosd
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(Original post by Anonymous_4657)
I'm stuck on this question. For the cylinder on the top I got the volume to be 6^2 π x 72. It this correct? The mark scheme says it is 36^2 π x 12.
The area of a circle is pi x radius^2, i think you've confused diameter and radius, so to get the right answer halve the diameter to get the radius, find the are of the circle, then multiply by the height to find the correct volume.
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Anonymous_4657
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(Original post by qwertyuiosd)
The area of a circle is pi x radius^2, i think you've confused diameter and radius, so to get the right answer halve the diameter to get the radius, find the are of the circle, then multiply by the height to find the correct volume.
isn't the diameter 12 so the radius must be 6. Also why does the mark scheme use 12 instead of 72??
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Anonymous_4657
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(Original post by qwertyuiosd)
The area of a circle is pi x radius^2, i think you've confused diameter and radius, so to get the right answer halve the diameter to get the radius, find the are of the circle, then multiply by the height to find the correct volume.
This is what the mark scheme says.
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Anonymous_4657
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(Original post by qwertyuiosd)
The area of a circle is pi x radius^2, i think you've confused diameter and radius, so to get the right answer halve the diameter to get the radius, find the are of the circle, then multiply by the height to find the correct volume.
Any luck with the question??
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Muttley79
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(Original post by Anonymous_4657)
This is what the mark scheme says.
I haven't looked at the mark scheme but I think the radius is 3.6 cm and the cylinder height 1.2 cm The flat fac would be lying against the hemisphere.
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Anonymous_4657
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(Original post by Muttley79)
I haven't looked at the mark scheme but I think the radius is 3.6 cm and the cylinder height 1.2 cm The flat fac would be lying against the hemisphere.
How did you get radius of 36mm and height of 12mm??
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Muttley79
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(Original post by Anonymous_4657)
How did you get radius of 36mm and height of 12mm??
The cylinder is upright - half of 72 mm = 3.6 cm
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Anonymous_4657
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(Original post by Muttley79)
The cylinder is upright - half of 72 mm = 3.6 cm
I though you work out the area of the circle at the end of the cylinder and times it by the length of the cylinder.
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Anonymous_4657
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(Original post by Anonymous_4657)
I though you work out the area of the circle at the end of the cylinder and times it by the length of the cylinder.
I think I've got it now.
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Muttley79
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(Original post by Anonymous_4657)
I though you work out the area of the circle at the end of the cylinder and times it by the length of the cylinder.
You do - the cylinder is upright ie the circular faces are top and bottom of the side view you can see.
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Anonymous_4657
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(Original post by Muttley79)
You do - the cylinder is upright ie the circular faces are top and bottom of the side view you can see.
I was imagining it as a tube lying length ways
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Muttley79
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(Original post by Anonymous_4657)
I was imagining it as a tube lying length ways
No - that would not made sense a tube lying on a hemisphere - they'd touch on a very small edge - not sensible for the context.
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Muttley79
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(Original post by Anonymous_4657)
I was imagining it as a tube lying length ways
Have you worked out the diagram now? I'll tag CoolCavy if not
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Anonymous_4657
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(Original post by Muttley79)
Have you worked out the diagram now? I'll tag CoolCavy if not
Thanks. I’ve worked it out now.
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