Question

The outer diameter of a glass cylinder is 20 cm find the cost of the painting of its outer covered surface at Rs 4 per square CM if the height of the cylinder is 70 cm

Answer 1

The total outer surface area of the cylinder with outer diameter  $D=20cm$ & height  $H=70cm$ is

$=\pi DH+2\times \frac{\pi}{4}D^2$  

$=\pi (20)(70)+\frac{\pi}{2}(20)^2$  

$=1600\pi cm^2$  

hence the cost of painting at a rate of Rs.4 per sq. cm is

$=1600\pi\times 4$  

$=6400\pi$  

$=Rs. 20106.19$