Arrange the following in descending order based on their perimeters:

A. A square with an area of 36 sq. cm.

B. An equilateral triangle with a side of 9 cm.

C. A rectangle with 10 cm as length and 40 sq. cm as area.

D. A circle with radius of 4 cm.

A $\rightarrow$ To find the perimeter of square, we need to find the length of side first.

Area $=$ (Side)$^2$ $= 36$ sq. cm.

Side $= 6$ cm.

Perimeter $= 4$ $\times$ Side $=24$ cm.

B $\rightarrow$ Perimeter of equilateral triangle is $3$ $\times$ Side

Perimeter $= 3 \times 9 = 27$ cm.

C $\rightarrow$ We need to find breadth of the rectangle first.

Area $=$ Length $\times$ Breadth $= 10$ $\times$ Breadth $= 40$ sq. cm.

Breadth $= 4$ cm.

Perimeter $= 2(l+b) = 2(10+4) = 28$ cm.

D $\rightarrow$ Perimeter of circle is $2\pi r$

Perimeter $= 2 \times \dfrac{22}{7} \times 4 = 25.14$ cm. $\text{(approx)}$

Perimeters in descending order $\rightarrow$ C > B > D > A