The figure shows 4 similar right-angled triangles arranged to form a big square which encloses a circle. The midpoints of the 4 sides of the big square touch the circumference of the circle. The two sides which form the right angle of each triangle are 48 cm and 36 cm respectively. Find the area of the shaded parts. (Take π = 3.14)
Difference in the length of the base and height of each triangle
= 48 - 36
= 12 cm
Area of the small square
= 12 x 12
= 144 cm
2 Area of the 4 triangles
=
12 x 36 x 48 x 4
= 3456 cm
2 Area of the big square
= 3456 + 144
= 3600 cm
2 Length of the big square
= √3600
= 60 cm
Radius of the big circle
= 60 ÷ 2
= 30 cm
Area of the big circle
= 3.14 x 30 x 30
= 2826 cm
2
Area of the 4 boomerangs
= 3600 - 2826
= 774 cm
2 Area of the shaded parts
= Area of the 2 boomerangs
= 774 ÷ 2
= 387 cm
2 Answer(s): 387 cm
2