A triangular pack `A B C` HAS SIDES `120 m ,\ 80 m\ a n d\ 50 m` . (See in 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 Rs. 20 per metre leaving a space `3m` wide for a gate on one side.

Explanation

Length of fence=perimeter of Triangle-`3m`

`=50+80+120-3`

`=247m`

Cost of wire=length`xx`cost

`=247xx20`

`=Rs.4940`

Herons formula

area=`sqrt(s(s-a)(s-b)(s-c))`

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