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Standard VIII

Mathematics

Surface Area of a Cuboid

A class is 7 ...

Question

A class is 7 m long, 6 m board and 3.5 m high. Doors and windows occupy an area of 17 $m^{2}$ . What is the cost of white-washing the walls at the rate of Rs. 1.50 per $m^{2}$ .

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Solution

Length of room (l) = 7 m
Breadth (b) = 6 m
and height (h) = 3.5 m
$∴$ Area of four walls = $2 (l + b) \times h$
= $2 (7 + 6) \times 3.5 m^{2} = 2 \times 13 \times 3.5 = 91 m^{2}$
Area of doors and windows = 17 $m^{2}$
\therefore Remaining area of walls = 91 -17 = 74 $m^{2}$
Rate of whitewashing = Rs. 1.50 per $m^{2}$
$∴$ Total cost = 74 $\times$ Rs. 1.50 = Rs. 111

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A class is 7 m long, 6 m board and 3.5 m high. Doors and windows occupy an area of 17 m2. What is the cost of white-washing the walls at the rate of Rs. 1.50 per m2.

A class is 7 m long, 6 m board and 3.5 m high. Doors and windows occupy an area of 17 $m^{2}$ . What is the cost of white-washing the walls at the rate of Rs. 1.50 per $m^{2}$ .