In a 30cm by 25cm rectangle, a quadrant of a circle of radius 7cm has been cut away from each corner. What is the perimeter of the part left? 

98cm

Explanation:

Dimension of rectangle = 30cm by 25cm

Length(l) = 30cm

Width(w) = 25cm

Perimeter of a rectangle = 2(l + w)

Quadrant of circle cut away of each side of the rectangle :

Radius = 7 cm =

That is, the dimension of the triangle reduces by 2 * 7 = 14cm

New length = 30 - 14 = 16cm

New width = 25 - 14 = 11cm

The four corners =( 4 × 2πr ) / 4

2πr = 2 × 22/7 × 7 = 44cm

Perimeter = 2(16cm + 11cm)

= 2(27cm)

Perimeter = 54cm + 44 = 98cm