Look at the cuboid below.
What is its surface area?
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Look at the cuboid below.
What is its surface area?
We identified that the faces are
3*3, 3*11, 11*3
As the opposite faces of an cuboid are equal, we know that for each face we find there is another face, therefore:
3*3, 3*11, 11*3
or
(3*3, 3*11, 11*3 ) *2
To find the surface area, we will have to add up all these areas, therefore:
(3*3+3*11+11*3 )*2
And this is actually the formula for the surface area!
We calculate:
(9+33+33)*2
(75)*2
150
150
A cuboid is shown below:
What is the surface area of the cuboid?
Because a cuboid has 6 faces total, but they come in 3 pairs of identical opposite faces. So you calculate one face of each type, then multiply by 2 to count both faces in each pair.
You still have 3 different face types! The faces are 3×3, 3×11, and 3×11. Even though two face types have the same area (33), you still need to count both pairs when calculating.
Imagine unfolding the cuboid like a cardboard box! You'll see:
Yes! Use the formula where l=length, w=width, h=height. For this problem:
Label the dimensions clearly! If it's 3×3×11, you have length=3, width=3, height=11. The three face types are: top/bottom (3×3), front/back (3×11), and left/right (3×11).
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