Student of class 12 presented a gift to their school in form of an electrical lamp in the shape of glass hemispherical base surmounted by a mettalic cylinderical top of same radius 21cm and hieght 3.5cm.the top was silver coated and glass surface was painted red.
1. What is the cost of silver coating the top at the rate of Rs 5/100cm2
Answers
Answered by
9
Step-by-step explanation:
Area of cylinder to be painted is = curved surface area
of cylinder + one base area
Given height of cylinder =3.5 cm
Radius =21cm
So by using formula
WE get area to be painted is 1848cm2
Cost of painting is (1848*5)/100=₹92.4
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Answered by
3
surface area to be painted red = 2772cm2
Step-by-step explanation:
Area to be coated with silver = 2πrh+πr2=πr(2h+r)
=22/7×21(7+21)
=66×28
=1848cm²
Cost of silver coating=1848/100 × 5
=92.5Rs
Surface area to be painted red = 2πr²
=2×22/7×21×21
=2772cm²
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