Surface area
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Surface area
Can anyone tell me how to calculate the surface area of a cuboid when laid flat. Obviously not the same as normally finding s/a.. Id really appreciate it if somebody would let me know. Many thanks
Re: Surface area
Do you mean when it is laid flat as a net?
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Re: Surface area
You have 3 measurements: length(L), width(W) and height(H).
You will have 2 each of:
L * W
L * H
W * H
Total surface area
2 * (L*(W+H) + (W*H))
You will have 2 each of:
L * W
L * H
W * H
Total surface area
2 * (L*(W+H) + (W*H))
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Re: Surface area
If your child finds it hard to visualize a net then they can just work out the area of 3 faces visible to them (this works for cubes and cuboids) and multiply each by 2 and then add them together.
cube - surface area = area of 1 face X 6
cuboid -
surface area = 2(L x H) + 2(L x W) + 2(H x W)
A cube is just 6 squares stuck together and a cuboid is 6 rectangles stuck together - when the child understands this, the calculation becomes really easy. Even if they forget the formula, they can quickly work out the answer.
cube - surface area = area of 1 face X 6
cuboid -
surface area = 2(L x H) + 2(L x W) + 2(H x W)
A cube is just 6 squares stuck together and a cuboid is 6 rectangles stuck together - when the child understands this, the calculation becomes really easy. Even if they forget the formula, they can quickly work out the answer.
Re: Surface area
Mummsie, didn't really understand your question. How can the same cuboid have two different surface areas?
Re: Surface area
That's what I was trying to work out.mystery wrote:Mummsie, didn't really understand your question. How can the same cuboid have two different surface areas?
Unless you have to work out the 'visible' surface area? I suppose in that case you would just not include the rectangle on the bottom, and then it would matter which end it was standing on.
The more that you read, the more things you will know.
The more that you learn, the more places you'll go. Dr Seuss
The more that you learn, the more places you'll go. Dr Seuss
Re: Surface area
But visible surface area would be what you could actually see from one particular point at any one time - so just 3 faces maximum - maybe only 1, depending upon your perspective.
I took it to mean the "area of the net laid flat" - which is equal to the surface area of the cuboid.
I took it to mean the "area of the net laid flat" - which is equal to the surface area of the cuboid.
Re: Surface area
Yes, I was just guessing. Don't anyone take my comment as an answer.
The more that you read, the more things you will know.
The more that you learn, the more places you'll go. Dr Seuss
The more that you learn, the more places you'll go. Dr Seuss
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Re: Surface area
It is the area of the net - I was just trying to explain the theory behind the calculation - assuming 3 faces are visible for a 3D shape.Okanagan wrote:But visible surface area would be what you could actually see from one particular point at any one time - so just 3 faces maximum - maybe only 1, depending upon your perspective.
I took it to mean the "area of the net laid flat" - which is equal to the surface area of the cuboid.
Your calculation is correct but I was trying to break down the logic if the child can't see it in their head as some children find it hard to visualize 3D objects without having a model to look at.
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Re: Surface area
mystery wrote:Mummsie, didn't really understand your question. How can the same cuboid have two different surface areas?
It would be the same as the measurements remain the same whether it is 3D or laid out flat as a net