Question
A wall is $4.5m$ long and $3m$ high. It has two equal windows, each having form and dimensions as shown in Figure. below. Find the cost of painting the wall (leaving windows) at the rate of $Rs. 15$ per $m^2$.
✓
Answer
We have,
Length of a wall $=4.5 m$
Breadth of the wall $=3 m$
Area of the wall $=$ Length $\times$ Breadth
$=4.5 m \times 3 m=13.5 m^2$
From the figure we observed that,
$\text { Area of the window }=\text { Area of the rectangle }+ \text { Area of the triangle }$
$=(0.8 m \times 0.5 m)+\left(\frac{1}{2} \times 0.8 m \times 0.2 m\right) \text { [Since } 1 m=100 cm \text { ] }$
$=0.4 m^2+0.08 m^2$
$=0.48 m^2$
Area of two windows $=2 \times 0.48=0.96 m^2$
Area of the remaining wall (leaving windows) $=(13.5-0.96) m ^2$
$=12.54 m^2$
Cost of painting the wall per $m ^2= Rs. 15$
Hence, the cost of painting on the wall $=$ Rs. $(15 \times 12.54)$
$=\text { Rs. } 188.1$
(In the book, the answer is given for one window, but we have $2$ windows.)
Length of a wall $=4.5 m$
Breadth of the wall $=3 m$
Area of the wall $=$ Length $\times$ Breadth
$=4.5 m \times 3 m=13.5 m^2$
From the figure we observed that,
$\text { Area of the window }=\text { Area of the rectangle }+ \text { Area of the triangle }$
$=(0.8 m \times 0.5 m)+\left(\frac{1}{2} \times 0.8 m \times 0.2 m\right) \text { [Since } 1 m=100 cm \text { ] }$
$=0.4 m^2+0.08 m^2$
$=0.48 m^2$
Area of two windows $=2 \times 0.48=0.96 m^2$
Area of the remaining wall (leaving windows) $=(13.5-0.96) m ^2$
$=12.54 m^2$
Cost of painting the wall per $m ^2= Rs. 15$
Hence, the cost of painting on the wall $=$ Rs. $(15 \times 12.54)$
$=\text { Rs. } 188.1$
(In the book, the answer is given for one window, but we have $2$ windows.)
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