a2zinterviews

19.	A right triangle with sides 3 cm, 4 cm and 5 cm is rotated about the side of 3 cm to form a cone. The volume of the cone so formed is
	A.  12Π cm3
	B.  15Π cm3
	C.  16Π cm3
	D.  20Π cm3

Solution

Clearly, we have r = 3cm and h = 4cm. ∴ Volume = 1/3Πr2h = (1/3 x Π x 32x4)cm3 = 12Πcm3.

20.	The total surface area of a solid hemisphere of diameter 14 cm is
	A.  308 cm2
	B.  462 cm2
	C.  1232 cm2
	D.  1848 cm2

Solution

Total surface area = 3ΠR2 = (3 x 22/7 x 7 x 7)cm2 = 462 cm2.

21.	Find the length of the longest pole that can be placed in a room 12 m long, 8 m broad and 9 m high.
	A.  10 m
	B.  12 m
	C.  17 m
	D.  19 m

Solution

Length of longest pole = Length of the diagonal of the room =√(12)2 + 82 + 92 ‹=›√289 = 17 m.