Ex 12.1, 3
There is a slide in the park. One of its side walls has been painted in the same colour with a message “KEEP THE PARK GREEN AND CLEAN” (see the given figure). If the sides of the wall are 15m, 11m, and 6m, find the area painted in green colour.
Area of triangle = √(s(s−a)(s−b)(s −c))
Here, s is the semi-perimeter,
and a, b, c are the sides of the triangle
Given sides of triangle 15 m, 6m , 11 m
So, a = 15 m, b = 6m , c = 11 m
s = (𝑎 + 𝑏 + 𝑐)/2
Area of triangle = √(𝑠(𝑠 −𝑎)(𝑠 −𝑏)(𝑠 −𝑐))
Putting a = 15 m, b = 6m , c = 11 m , s = 16 m
=√(16(16−11)(16−6)(16−15)) m2
= √(16×5×10×1) m2
= √16×√(5×10) m2
= √16×√(5×5×2) m2
= √16×√(5×5) " "×√2 m2
= √42×√52 " "×√2 m2
= 4 × 5 ×√2 m2
= 20 √2 m2
Therefore, the area painted in colour is = 20 √2 m2 .

Made by

Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 12 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.

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