Look at the cuboid below.
What is the surface area of the cuboid?
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Look at the cuboid below.
What is the surface area of the cuboid?
Let's see what rectangles we have:
8*5
8*12
5*12
Let's review the formula for the surface area of a rectangular prism:
(length X width + length X height + width X height) * 2
Now let's substitute all this into the exercise:
(8*5+12*8+12*5)*2=
(40+96+60)*2=
196*2= 392
This is the solution!
392 cm²
A cuboid is shown below:
What is the surface area of the cuboid?
A cuboid has 6 faces arranged in 3 pairs of opposite faces. Each pair has identical dimensions: two 8×5 faces, two 8×12 faces, and two 5×12 faces. So you calculate one of each pair, then multiply by 2!
That works too! You'd get 8×5 + 8×5 + 8×12 + 8×12 + 5×12 + 5×12 = 392. The formula 2(lw + lh + wh) is just a shortcut to avoid writing each face twice.
It doesn't matter which dimension you call length, width, or height! The formula works the same way. In this problem: 8, 5, and 12 can be assigned to l, w, h in any order.
Surface area is always measured in square units (like cm², m², ft²). Since we're multiplying two lengths together for each face area, the result is length × length = length².
Yes! This formula 2(lw + lh + wh) works for any cuboid or rectangular prism, whether it's a box, room, or building block. Just substitute your three dimensions.
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