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Home » A factory manufactures 120000 pencils daily. The pencils are cylindrical in shape each of length 25 cm and circumference of base as 1.5 cm. Determine the cost of colouring the curved surfaces of the pencils manufactured in one day at Rs 0.05 per dm2.
A factory manufactures 120000 pencils daily. The pencils are cylindrical in shape each of length 25 cm and circumference of base as 1.5 cm. Determine the cost of colouring the curved surfaces of the pencils manufactured in one day at Rs 0.05 per dm2.
CBSE | Class 10 | Maths | NCERT Exemplar | Surface Areas And Volumes
A factory manufactures 120000 pencils daily. The pencils are cylindrical in shape each of length 25 cm and circumference of base as 1.5 cm. Determine the cost of colouring the curved surfaces of the pencils manufactured in one day at Rs 0.05 per dm2.

The state of pencil = chamber.

Let the sweep of base = r cm

Outline of base = 1.5 cm

Boundary of circle is 2πr = 1.5 cm

r = 1.5/2π cm

As per the inquiry,

Tallness, h = 25 cm

We realize that,

Bended surface space of chamber = 2πrh

Bended surface space of pencil

    \[=\text{ }2\pi \text{ }\left( 1.5/2\pi \right)\text{ }25\text{ }=\text{ }37.5\text{ }cm2\]

1 cm = 0.1 dm

1 cm2 = 0.01 dm2

37.5 cm2 = 0.375 dm2

Cost for shading 1 dm2 = Rs. 0.05

Cost for shading 0.375 dm2 (for example 1 pencil) = Rs. 0.01875

Cost for shading 120000 pencils = 120000 ×0.01875 = Rs. 2250

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