Looking at the way the rectangles are arranged, you can see that the length of each rectangle is exactly four times the breadth/width of each rectangle.

The 70 cm presented in the diagram is made up of one breadth and one length - this is an equivalent of five breadths.

Breadth of rectangle
= 70 / 5
= 14 cm

The circle has a diameter equal to three breadths long, or 42 cm long.

Its radius is half of this, or 21 cm long.

Area of that circle
= pi x radius x radius
= 3.14 x 21 x 21
= 1384.74 cm²

Thanks