Write True or False and justify your answer:
If the radius of a right circular cone is halved and height is doubled, the volume will remain unchanged.
Write True or False and justify your answer:
The volume of a sphere is equal to two-third of the volume of a cylinder whose height and diameter are equal to the diameter of the sphere.
The radius of a hemispherical balloon increases from 6 cm to 12 cm as air is being pumped into it. The ratios of the surface areas of the balloon in the two cases is
(A) 1 : 4 (B) 1 : 3 (C) 2 : 3 (D) 2 : 1
The length of the longest pole that can be put in a room of dimensions (10 m × 10 m × 5m) is
(A) 15 m (B) 16 m (C) 10 m (D) 12 m
The number of planks of dimensions (4 m × 50 cm × 20 cm) that can be stored in a pit which is 16 m long, 12m wide and 4 m deep is
(A) 1900 (B) 1920 (C) 1800 (D) 1840
The radii of two cylinders are in the ratio of 2:3 and their heights are in the ratio of 5:3. The ratio of their volumes is:
(A) 10 : 17 (B) 20 : 27 (C) 17 : 27 (D) 20 : 37
In a cylinder, radius is doubled and height is halved, curved surface area will be
(A) halved (B) doubled (C) same (D) four times
A cone is 8.4 cm high and the radius of its base is 2.1 cm. It is melted and recast into a sphere. The radius of the sphere is :
(A) 4.2 cm (B) 2.1 cm (C) 2.4 cm (D) 1.6 cm
In a cylinder, if radius is halved and height is doubled, the volume will be
(A) same (B) doubled (C) halved (D) four times
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