SURFACE AREAS
AND VOLUMES
Q. A bucket in the form of a frustum of a cone and holds
28.490 litres of water. The radii of the top and bottom are 28 cm and
21 cm respectively. Find the height of the bucket.
28cm
21cm
?
Sol.
Let the height of the bucket be h cm.
r1
=
28 cm,
r2
=
21 cm,
Volume of the bucket
=
28.490 litres
=
28.490
×
1000
=
28490 cm3
Volume of the bucket
1
3
πh
=
28490
1
3
×
22
7
×
h
×
(282
22
21
×
h
×
(784
=
28490
28cm
21cm
Let the radius of
top face be r1
h = ?
Let the radius of
bottom face be r2
We know,
1 litre = 1000 cm3
+ 212)
+ 588
+ 441)
What is the formula to find volume of the frustum?
1
3
πh
Let us convert litres into cm3
Volume of the frustum =
+ 28
× 21
Q. A bucket in the form of a frustum of a cone and holds
28.490 litres of water. The radii of the top and bottom are 28 cm and
21 cm respectively. Find the height of the bucket.
28cm
21cm
h = ?
h
=
28490
×
21
22
×
1813
h
=
15 cm
22
21
×
h
×
1813
=
28490
15 cm
Height of the bucket is 15 cm
∴
22
21
×
h
×
(784
=
28490
+ 588
+ 441)
2590
3
259
h
=
2590
×
3
2
×
259
2
10
5
Sol.
Q. A bucket in the form of a frustum of a cone and holds
28.490 litres of water. The radii of the top and bottom are 28 cm and
21 cm respectively. Find the height of the bucket.
∴
∴
∴
∴