Question

A factory manufacturer 120000 pencil daily the pencil are cylinder in shape each of length 25 cm and circumference of base as 1.5 cm determine the cost of colours the curved surface of the pencil manufacturer in one day at Rs 0.05 per dm2

Answer 1

The surface area of one pencil = 25x1.5 = 37.5 cm²
 the total surface area of pencils made in a day =  37.5 x 120000
                                                                           = 45000000cm²
                                                                           = 45,000dm²

The cost of colours = 45,000 x 0.05 = Rs. 2,250

Note:
1dm² = 100cm²

Answer 2

Given:
Circumference of 1 pencil base(2πr)= 1.5cm
Length or height of 1 pencil(h)=25cm
Curved surface Area of cylinder(CSA) = 2πrh
CSA of 1 pencil =(2πr)h = 1.5× 25
CSA of 1 pencil = 37.5 cm²
CSA of 1 pencil =0.375 dm²
[1cm² = 1/100 dm²]
Factory manufactured pencil in one day= 120,000
Total CSA of 120000 pencils= 120,000×0.375
Total CSA of 120000 pencils= 45,000 dm²
Cost of colouring one pencil= ₹ 0.05
Total cost of 120000 pencils = 45,000× 0.05
=₹ 2,250.

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