Example 2 : A triangular park ABC has sides 120m, 80m and 50m (see Fig

1.	Example 2 : A triangular park ABC has sides 120m, 80m and 50m (see Fig. 8.7). Agardener Dhania has to put a fence all around it and also plant grass inside. Howmuch area does she need to plant? Find the cost of fencing it with barbed wire at therate of Rs 20 per metre leaving a space 3m wide for a gate on one side.
Answer» Let a=120m b=80m c=50m s=a+b+c/2 =120+80+50/2 =250/2 =125m From heron's formula Area of triangle=√s(s-a)(s-b)(s-c) =√12554575 =√5555533553 =375√15m2 Perimeter of trianglular park=250m Space left for fencing=250-3 =247m Cost of fencing 247m=247*20 =Rs.4940

Example 2 : A triangular park ABC has sides 120m, 80m and 50m (see Fig. 8.7). Agardener Dhania has to put a fence all around it and also plant grass inside. Howmuch area does she need to plant? Find the cost of fencing it with barbed wire at therate of Rs 20 per metre leaving a space 3m wide for a gate on one side.

Answer»

Let a=120m b=80m c=50m

s=a+b+c/2

=120+80+50/2

=250/2

=125m

From heron's formula

Area of triangle=√s(s-a)(s-b)(s-c)

=√125*5*45*75

=√5*5*5*5*5*3*3*5*5*3

=375√15m2

Perimeter of trianglular park=250m

Space left for fencing=250-3

=247m

Cost of fencing 247m=247*20

=Rs.4940