A cylinder lenght 13cm and radius 5cm is made of cardboard .use the value of 3.1 py at (a) a closed cylinder (b) a cylinder open at one side
I assume you want to find the surface area
a) two circle + a rectangle
= 2π(5^2) + 2π(5)(13)
= 50π + 130π
= 180π
= appr 565.49 cm^2
(Nobody would use π as 3.1 in 2015)
b) if it is open at one end, the use only one circle
and repeat my steps
To find the surface area of the cylinder, we can use the formula:
(a) Surface Area of a Closed Cylinder:
The surface area of a closed cylinder is given by the formula: 2πr(r+h), where r is the radius and h is the height (or length) of the cylinder.
In this case, the radius (r) is 5 cm and the height (h) is 13 cm. Using the value of π as 3.1, we can substitute these values into the formula:
Surface Area = 2 * 3.1 * 5 * (5 + 13)
Surface Area = 2 * 31 * 18
Surface Area = 1116 cm²
Therefore, the surface area of the closed cylinder is 1116 cm².
(b) Surface Area of a Cylinder Open at One Side:
In this case, since the cylinder is open at one side, we need to subtract the base area from the surface area of the closed cylinder.
The base area of a cylinder is given by the formula: πr², where r is the radius.
Using the radius (r) as 5 cm, we can find the base area:
Base Area = 3.1 * 5 * 5
Base Area = 78.5 cm²
Now, subtracting the base area from the surface area of the closed cylinder, we get:
Surface Area = 1116 - 78.5
Surface Area = 1037.5 cm²
Therefore, the surface area of the cylinder open at one side is 1037.5 cm².