Question

8. A door of length 2 m and breadth Im is fitted ink wall. The length of the
wall is 4.5 m and the breadth is 3.6 m (Fig.1.6). Find the cost of white
washing the wall, if the rate of white washing the wall is 20 per m.​

Answer 1

Question :

A door of length 2 m and breadth 1 m is fitted in the wall. The length of the wall is 4.5 m and the breadth is 3.6 m. Find the cost of white washing the wall, if the rate of white washing the wall is 20 per m.

Given :

• Length of the door (l) = 2 metre
• Breadth of the door (b) = 1 metre
• Length of the wall (L) = 4.5 metre
• Breadth of the wall (B) = 3.6 metre
• Cost for white washing 1 metre of wall = Rs.20

Explanation :

• The door and wall was in the form of rectangle , hence we can find the area of white washing the wall by using area of rectangle formula.

$\underline{\boxed{\sf{Area_{(Rectangle)}=length \times breath}}}$

• It's given to find the cost for white washing wall. Hence, we have to find the area of wall without measuring the area of door. So we have to reduce the area of door from area of the wall.

$\underline{\boxed{\sf{Area_{(Washable\: Surface\:in\: wall)}=Area_{(Wall)}-Area_{(Door)}}}}$

Solution :

Area of Wall = length × Breadth

$\rightarrow \sf L \times B$

$\rightarrow \sf 4.5 \times 3.6$

$\rightarrow \sf 16.2m^2$

Area of Door = length × breadth

$\rightarrow \sf l \times b$

$\rightarrow\sf 2 \times 1$

$\rightarrow \sf 2m^2$

Area of white washing the wall = Area Of wall - Area of door

$\sf \rightarrow 16.2m^2 - 2m^2$

$\rightarrow \sf 14.2m^2$

Cost for White washing the wall = Area of the wall × Cost for washing 1 metre

$\sf \rightarrow 14.2 m^2\times Rs.20$

$\sf \rightarrow 285$

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Required Answer :

Cost for white washing the wall is $\sf underline{Rs. 285}$

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