Question

A triangular park $ABC$ has sides $120m,80m$ and $50m$ (see figure). A gardener Dhania has to put a fence all around it and also plant grass inside. How much area does she need to plant? Find the cost of fencing it with barbed wire at the rate of $Rs20$ per metre leaving a space $3m$ wide for a gate on one side ?

Answer 1

here, $a=120m,b=80m,c=50m$

and, $s=\frac{a+b+c}{2}=\frac{250}{2}=125$

Area she need to plant grass $=\sqrt{s(s-a)(s-b)(s-c)}=\sqrt{125(125-120)(125-80)(125-50)}=375\sqrt{15}{m}^2$

cost of fencing $=[(a+b+c)-3].20=[250-3].20=Rs4940$