Mohan wanted to paint the walls and ceiling of a hall- The dimensions of the hall are 20 m - 15 m - 6 m- Find the area of the surface to be painted and the cost of painting it at Rs- 78 per square meter-

Area to be painted = Total surface area of the cuboid Area of the floor #160; #160; #160; #160; #160; #160; #160; #160; ...

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Byju's Answer

Standard IX

Mathematics

Volume of a cuboid

Mohan wanted ...

Question

Mohan wanted to paint the walls and ceiling of a hall. The dimensions of the hall are $20 m$ $\times$ $15 m$ $\times$ $6 m .$ Find the area of the surface to be painted and the cost of painting it at $R s . 78$ per square meter.

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Solution

Area to be painted $=$ Total surface area of the cuboid $-$ Area of the floor
$= 2 (l b + b h + l h) - l b$ (Since the floor won't be painted)
$= 2 (20 \times 15 + 15 \times 6 + 20 \times 6) - 20 \times 15$
$= 2 (300 + 90 + 120) - 300$
$= 1040 - 300$
$= 720 m^{2}$
Cost of painting $=$ Cost per $m^{2} \times$ Area in $m^{2}$
$= 78 \times 720$
$= R s . 56160$

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Mohan wanted to paint the walls and ceiling of a hall. The dimensions of the hall are 20 m × 15 m × 6 m. Find the area of the surface to be painted and the cost of painting it at Rs. 78 per square meter.

Area to be painted = Total surface area of the cuboid − Area of the floor =2(lb+bh+lh)−lb (Since the floor won't be painted) =2(20×15+15×6+20×6)−20×15 =2(300+90+120)−300 =1040−300 =720 m2Cost of painting = Cost per m2 × Area in m2 =78×720 =Rs. 56160

Mohan wanted to paint the walls and ceiling of a hall. The dimensions of the hall are $20 m$ $\times$ $15 m$ $\times$ $6 m .$ Find the area of the surface to be painted and the cost of painting it at $R s . 78$ per square meter.