Chapter 10 - Radical Expressions and Equations - 10-4 Solving Radical Equations - Practice and Problem-Solving Exercises - Page 623: 18

$A=486$ $cm^{2}$

$Given,$ $s=9$ $cm$ $9$ $cm=\sqrt \frac{A}{6}$ Squaring,we get: $81$$cm^{2}=\frac{A}{6}$ $A=81X6cm^{2}=486cm^{2}$ We need to check by putting the obtained value in the original equation : $R.H.S=\sqrt \frac{486}{6}=\sqrt 81=9$ $cm=L.H.S$ Hence,$A=486$ $cm^{2}$ is a valid solution