Question
question A wall is 4.5 m long and 3 m 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,
Area of the window $=$ Area of the rectangle + Area of the triangle
$=(0.8 m \times 0.5 m)+\left(\frac{1}{2} \times 0.8 m \times 0.2 m\right)[\text { Since } 1 m=100 cm]$
$=0.4 m^2+0.08 m^2$
$=0.48 m^2$
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,
Area of the window $=$ Area of the rectangle + Area of the triangle
$=(0.8 m \times 0.5 m)+\left(\frac{1}{2} \times 0.8 m \times 0.2 m\right)[\text { Since } 1 m=100 cm]$
$=0.4 m^2+0.08 m^2$
$=0.48 m^2$
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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