Question

find the cost of painting the outside surface of a solid cylinder of diameter 14 m and height 21 m at rupees 8 per metre square​

Answer 1

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Diameter of solid cylinder = 14m

Radius = 14m ÷ 2 = 7m

Height = 21m

Curved Surface Area of solid cylinder

$2\pi \: rh \\ = 2 \times \frac{22}{7} \times 7m \times 21m \\ = 2 \times 22 \times 1m \times 21m \\ = 924 {m}^{2}$

Cost of Painting/per m² = ₹8

924m² will cost = 924m² × ₹8 = ₹7,392

Hence, Cost of painting = ₹7,392

Answer 2

The cost of painting the outside surface of a solid cylinder is Rs. 9856.

Step-by-step explanation:

Diameter of the cylinder=14m

So radius=7m

Height of the cylinder=21m

We have to color the outside of the cylinder which means surface area.

The surface area of the cylinder=2πr(h+r)

                                                     =2×$\frac{22}{7}$×7m(21m+7m)

                                                     =2×$\frac{22}{7}$×7m(28m)

                                                      =1232$m^{2}$

cost of painting per meter square= Rs. 8

So total cost=1232$m^{2}$×8=Rs. 9856