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Example 2 :A triangular park ABC has sides 120m, 80m and 50m (see Fig. 12.7).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. |
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Answer» Given the sides of the triangular park are 120m, 80m and 50m. perimeter of the triangular park = 120m + 80m + 50m= 250m therefore it's semi-perimeter = 250/2= 125mhence, the gardener have to plant grass in 1452.36m²Area of triangular park by heron formula=√s(s-a)(s-b)(s-c)=√125(125-120)(125-80)(125-50)=√2109375=1452.36m^2 now we have to find the cost of fencing the field with a barbed wire at the rate of rs 20 per m leaving a space of 3m wide for a gate. therefore the gardener have to fence = 250 - 3= 247m so total cost of fencing at the rate of rs 20 per meter = 247 × 20= rs 4940 thanks bhaiya |
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