Students of a school staged a rally for cleanliness campaign. They walked through the lanes in two groups. One group walked through the lanes `AB`, `BC` and `CA`; while the other through `AC`, `CD` and `DA` (see Fig. 12.12). Then they cleaned the area enclosed within their lanes. If `AB = 9 m`, `BC = 40 m`, `CD = 15 m`, `DA = 28 m` and `/_ B = 90^@`, which group cleaned more area and by how much? Find the total area cleaned by the students (neglecting the width of the lanes).

Explanation

Area`ABC=1/2xxBCxxAB`

`1/2xx40xx9=180m^2`

By Pythagoras Theorem

`AC^2=AB^2+BC^2`

`AC^2=9^2+40^2`

`AC^2=1681`

`AC=41m`

s=(a+b+c)/2=84/2=42

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