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 40 cm and 30 cm respectively. Find the area of the shaded parts. (Take π = 3.14)
= 40 - 30
= 10 cm

Area of the small square
= 10 x 10
= 100 cm²

Area of the 4 triangles
= ¹₂ x 30 x 40 x 4
= 2400 cm²

Area of the big square
= 2400 + 100
= 2500 cm²

Length of the big square
= √2500
= 50 cm

Radius of the big circle
= 50 ÷ 2 
= 25 cm

Area of the big circle
= 3.14 x 25 x 25
= 1962.5 cm²

Area of the 4 boomerangs
= 2500 - 1962.5
= 537.5 cm²

Area of the shaded parts
= Area of the 2 boomerangs
= 537.5 ÷ 2 
= 268.75 cm²

Answer(s): 268.75 cm²