Answer:
150 m²
Explanation:
You want the total area of a figure consisting of a 12 m wide rectangle 5 m high with a triangle above that bringing the total height to 20 m.
Rectangle area
The area of the rectangle is the product of its length and width:
A = LW
A = (12 m)(5 m) = 60 m²
Triangle area
The area of the triangle is half the product of its base and height.
A = 1/2bh
A = 12/(12 m)(20 -5 m) = 90 m²
Total area
The area of the whole figure is the sum of the areas of its parts:
total area = rectangle area + triangle area
total area = 60 m² +90 m² = 150 m²
The area of the figure is 150 m².
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Additional comment
Since you know a triangle's area is equivalent to the area of a rectangle that has half the height, the 15 m high triangle can be considered as a rectangle 7.5 m high. Adding that to the 5 m area of the rectangle already there gives the equivalent area as that of a rectangle 12 m wide and 5+7.5 = 12.5 m high: (12 m)(12.5 m) = 150 m².
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