Question

Anyone please help me with this GEOMETRY QUESTION?

Andre made a wax model of a rolling pin of diameter 4 cm. The rolling pin was shaped like a right circular cylinder with a right circular cone at each end as shown below.



What was the total surface area of the rolling pin? Using complete sentences, describe the steps you used to calculate the surface area.

Answer 1

@mathstudent55

Do you know this?

Answer 2

There are three parts to the total surface are. One is the cylindrical part in the middle. The other two are the cones at the ends.
Starting with the cylindrical part, you need the suface area of a cylinder of radius 2 cm and height 13 cm. That is calculated by multipling the circumference of the base of the cylinder by the height. A = 2(pi)rh, where area is the lateral area of the cylinder (not including the bases), r is the radius of the base and h is the height.
Then you have the area of the cones at the ends. The formula there is A = (pi)rs, where r is the radius of the cone and s is the diagonal length which is 7 cm in your problem.
Remember there are two cones, so you need to multiply the area of the cone by 2.

A = 2(pi)rh + 2 x (pi)rs
A = 2 x 3.14159 x 2 x 13 + 2 x 3.14159 x 2 x 7 = 251.33 cm^2