Question

11. The inner circumference of a hollow cylindrical pipe is 4.5 m and outer circumference is 4.6 m. Find the cost
of painting both its inner and outer sides at the rate of 20 per m', if it is 8 m tall
​

Answer 1

Answer:

Step-by-step explanation:

Area of Inner surface of Pipe:        

C = 2$\pi$r

r = $\frac{4.5 * 7}{22 * 2 * 8 }$

A. of inner cyl. =

2$\pi$rh + 2$\pi$$r^{2}$

= 4.5 * 8 + 2 *$\frac{22}{7}$ * $\frac{4.5 * 7}{22*2*8}$

= 36.5625 $m^{2}$

Area of Outer Surface of pipe:

C = 2$\pi$r

r = $\frac{4.5 * 7}{22 * 2 * 8 }$

A. of outer cyl. =

2$\pi$rh + 2$\pi$$r^{2}$

= 4.6 * 8 + 2 *$\frac{22}{7}$ * $\frac{4.6*7}{22*2*8}$

= 36 + 0.575

= 36.575

Total suarface area :

36.5625 + 36.575 = 73.1375$m^{2}$

therefore,

20 * 73.135 = 1462.75

so, it takes 1462.75 amount of money to paint the cylindrical pipe.