Question

A cylindrical wall is 21cm deep . Its outer and inner diameter are21cm and 14cm respectively. Find the cost of inovating the inner and outer curved surface at the rate of 25 per square metre

Answer 1

Ans. Rs.1,155
Step by Step Explanation.
Given: Height(h) of cylinder= 21 cm
Outer Radius(R)= 21 cm
Inner Radius(r) = 14 cm
We have to find total curved surface area of cylindrical wall:
so, Total curved Surface Area= External curved surface area+ internal curved surface area.
External curved surface area of cylinder= 2pieRh
= 2×3.14×21×21= 2772cm or 27.72m.
Internal curved surface area of cylinder=
2pie rh
= 2×3.14×14×21= 1848cm or 18.48 m
So, Total curved surface area of cylindrical wall= 27.72m+ 18.48m
= 46.2m²
It is given the cost of renovating per square meter of cylindrical wall is Rs 25.
Therefore, cost of renovating 46.2 m²= 46.2×25= 1,155
Hence, Ans. Rs. 1,155.
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