[tex]length \: of \: 1 \: side = diameter[/tex]
[tex]area \: = {l}^{2} \\ 100 = {l}^{2} \\ \sqrt{100} = l \\ l = 10[/tex]
[tex]diameter = 2 \times radius \\ 10 = 2 \times radius \\ radius = 5[/tex]
[tex]circle \: area = pi \times {r}^{2} \\ circle \: area = 3.142 \times {5}^{2} \\ circle \: area = 3.142 \times 25 \\ circle \: area = 78.55 {cm}^{2} [/tex]
