Question

A cubical box with lid has a length of 30 find the cost of panting the inside and outside of the box at the rate of 5.50rupees per m2

Answer 1

Surface area of the cube = 6a²  where a = 30 cm

⇒ 6*30*30

⇒ 5400 sq cm

As the cubical box has to be painted both from the outside and inside.

So, the total surface area = Inner surface area + outer surface area

⇒ 5400 + 5400 

= 10800 sq cm

As we know that 1 sq m = 10000 sq cm

Surface area in sq m = 10800/10000

Surface area in sq m = 1.08 sq m

Cost of painting the cubical box = Rs. 5.50 per sq m

Total cost of painting = 5.5*1.08

Total cost = Rs. 5.94

So, the total cost of painting the cubical box from outside and inside is Rs. 5.94.

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Answer 2

Since it's a cube, then all the sides would be equal.... Now, according to the question....

Length of one side the cube is 30 cm = 0.3 m

Since it has to be painted inside as well as outside, we have to find the TSA of the cube two times.....and the TSA of a cube is 6a²..

∴Total area of the cube to be painted = 2 × 6a²

⇒2 × 6 × (0.3)² m²

⇒2 × 6 × 0.09 m²

⇒2 × 0.54 m²

⇒1.08 m²

Now, the cost of painting per m² of cube = Rp. 5.50

⇒1.08 m² × Rp. 5.50

⇒Rp. 5.94