The given figure consists of and four small semi-circles of A B equal; radii and two big len semi-circles of equal radii (each 42 cm). Find the area and perimeter of Two the shaded region 25. In 19. The total surface area of a hollow cylinder which is open from both sides is 3575 cm

Explanation

Area of shaded region = `2(`Area of bigger semicircle`-` Area of smaller semi circle `+` Area of smaller semi circle`)`

`= 2(` Area of bigger semi circle`)`

`= 2((pi r^2)/2) = pir^2 = 22/7**42**42 = 5544 cm^2`

Now,

Perimeter of the shaded region `= 2(`Perimeter of bigger semicircle `+ 2*`Perimeter of smaller semicircle`)`

`= 2[pir+2*(pi(r)/2)]`

`=4pir = 4*22/7*42 = 528cm.`