Question

an open cylindrical oil tank has diameter 14 metre and height 9 if the inner side of the tank has to be painted all over what will it cost as rupees 40 per square metre​

Answer 1

Cost of painting is 15840 Rupees.

Step-by-step explanation:

1. Given data

   Height of cylinder (H) = 9 m

   Diameter of cylinder (D) = 14 m

   Radius of cylinder (R) = 7 m

   $\mathbf{\textrm{ Rate of painting} =40 \ \frac{Rs}{m}}$

2. $\mathbf{\textrm{ Inner surface area } =2\times \pi \times R\times H}$            ...1)

   $\mathbf{\textrm{Here} \ (\pi) =\frac{22}{7}}$  

   So

   $\mathbf{\textrm{ Inner surface area } =2\times \frac{22}{7} \times 7\times 9}$

   $\mathbf{\textrm{ Inner surface area } =396 \ m^{2}}$

3. Cost of painting = Inner surface area × Rate of painting

   Cost of painting = 396 × 40 =15840 Rupees