There is a slide in a park. One of its side walls has been painted in some colour with a message KEEPTHE PARK GREENAND CLEAN" (see Fig. 12.10). If the sides of the wall are $ 15 \mathrm{~m}

AcademicMathematicsNCERTClass 9

Given:

The sides of the wall are $15\ m, 11\ m$ and $6\ m$.

To find:

We have to find the area of the painted wall in colour.

Solution:

The sides of the wall are $15\ m, 11\ m$ and $6\ m$.

By Heron's formula:

$A=\sqrt{s(s-a)(s-b)(s-c)}$

Since,

$S=\frac{a+b+c}{2}$

$S=\frac{15\ m+11\ m+6\ m}{2}$

$S=\frac{32\ m}{2}$

$S=16\ m$

This implies,

$A=\sqrt{16(16-15)(16-11)(16-6)}$

$A=\sqrt{16(1)(5)(10)}$

$A=\sqrt{800}\ m^2$

$A=20\sqrt2\ m^2$

Therefore,

The area of the painted wall in colour is $20\sqrt2\ m^2$.

raja
Updated on 10-Oct-2022 13:41:58

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