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Question
A factory manufactures 120,000 pencils daily . The pencil 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 ₹0.05 per dm2.
Solution
Length of the pencil, h = 25 cm
circumference of the base = 1.5 cm
Curved surface area of the pencil which needs to be painted will be
\[\text { CSA = circumference } \times \text { height }\]
\[ = 1 . 5 \times 25 c m^2 \]
\[ = 37 . 5 c m^2\]
= 0.375 dm2
Pencils manufactured in one day = 120000
So, the total area to be painted will be \[120000 \times 0 . 375 d m^2 = 45000 d m^2 \]
Cost of painting this area will be \[45000 \times 0 . 05 = \text { Rs }.2250\]
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