What is the surface area of this design? 5 in.
5 in.
490 in2
8 in.
8
600 in2
560 in 2
2 in.
440 in2
10 in.
10 in.

You probably already know that the tall rectangles take up 4×(5×8)=160 of surface area, and that the short rectangles take up 4×(2×10)=80 of surface area. This looks like an office building so let's call it one.

You probably also saw the big, 10×10=100 inch area underneath the design.

BUT, did you know that the small, 5×5 inch square on top can be COMBINED with the weird, L-shaped flat-roof part in the middle? That's right! the 5×5 inch square can be seen as part of a full 10×10 inch square sitting on top of the short, wide rectangles.

If you look at the L-shaped flat roof, you can see that it's actually 3 more 5×5 squares. You need to connect the 10-inch dimension on the bottom with the 5-inch one on the top.

SO, the answer is gonna be:

160 in² in tall rectangles, +

80 in² in short rectangles, +

100 in² on the bottom, +

100² on the combined top small square and corner roof

Add those all up using some quick maths, and you get 440 in².

Some more details if you're still confused:

The sides of the tall rectangle? It's 5 inches by 8 inches, so each side 8×5=40 in². They go all around the tall box, so there are 4 of them. 40+40+40+40=160, or in other words, 40×4=160.

Do you see the short, wide rectangles on the bottom? they're 10 inches by 2 inches each, so each one is 2×10=20 in². They also go all around the short box, so they add up to 20+20+20+20=80, or in other words, 20×4=80.

Now I want you to think about the bottom of the design, underneath. It is 10 inches by 10 inches, so it is 10×10=100.

Finally, the small square on top of the tall rectangle, and that L-shaped part. Together, they make another 100, or 5×5 on top plus 5×10 + 5×5 again for the parts of the L-shaped roof, or 25+50+25, which equals 100.

Step-by-step explanation:

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