Step-by-step explanation:
we have one large rectangle and 2 small right-angled triangles to add.
the area of the rectangle is easy : 15×25 = 375
the right-angled triangle on the long side has one side = 5, and the "invisible" side is 25 - 12 - 5 = 8.
these 2 sides are hitting each other in a right angle and can therefore be used as baseline and height of the triangle.
the area of a triangle is baseline×height/2.
so, the area of the this triangle is 8×5/2 = 20.
the right-angled triangle on the right short side has one side = 5, and the "invisible" side is 15 - 10 = 5.
these 2 sides are hitting each other in a right angle and can therefore be used as baseline and height of the triangle.
so, the area of the this triangle is 5×5/2 = 12.5.
so the total area is
375 + 20 + 12.5 = 407.5
