SURFACE AREAS
AND VOLUMES
Q. A wooden article was made by scooping out a hemisphere from
each end of a solid cylinder, as shown in figure. If the height of
the cylinder is 10cm, and its base is of radius 3.5 cm,
find the total surface area of the article.
CSA of the cyl. (S1)
Sol.
= 2 π r h
= 2 × π
= 70π cm2
× 3.5
× 10
CSA of 2 hemispheres (S2)
= 2 × 2πr2
= 2 × 2 × π
= 49π cm2
× (3.5)2
The wooden article is made
by scooping out hemispheres from each end of the cylinder
What is the formula to find curved surface area of cylinder?
What is the formula to find curved surface area of hemisphere ?
TSA of article =
CSA of cylinder (S1) +
2 CSA of hemisphere (S2)
2 π r h
2 π r2
✔
✔
✔
= 7
× 10
× π
= 4
× π
× 12.25
∴ CSA of the cyl. (S1)
∴ CSA of 2 hemispheres (S2)
10 cm
3.5cm
22
7
S1 + S2
17
TSA of the article =
= 70π
= 119π
= 119 ×
= 374 cm²
TSA of the article is 374 cm2
+ 49π
∴
Q. A wooden article was made by scooping out a hemisphere from
each end of a solid cylinder, as shown in figure. If the height of
the cylinder is 10cm, and its base is of radius 3.5 cm,
find the total surface area of the article.
Sol.
TSA of article =
CSA of cylinder (S1) +
2 CSA of hemisphere (S2)
2 π r h
2 π r2
S1 = 70π
S2 = 49π
10 cm
3.5cm