Chapter 13: Surface Areas and Volumes

Q1. In a cylinder, if radius is halved and height is doubled, the volume will be
(A) same            (B) doubled               (C) halved              (D) four times
Solution:  (C)

Q2.The radius of a sphere is 2r, then its volume will be
(A) 43πr³        (B) 4πr³             (C) 83πr³  (D)  323πr³
Solution:

Q3.The total surface area of a cube is 96 cm² . The volume of the cube is:
(A) 8 cm³        (B) 512 cm³          (C) 64 cm³         (D)  27 cm³
Solution:

Q4. 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
Solution:

Q5.In a cylinder, radius is doubled and height is halved, curved surface area will be

(A) halved         (B) doubled              (C) same          (D) four times
Solution:

Q6.The total surface area of a cone whose radius is r2 and slant height 2l is
(A)  2πr(l+r)              (B)  πrl+r4
(C) πr(l+r)                        (D) 2πrl
Solution:

Q7.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
Solution:

Q8.The lateral surface area of a cube is 256 m². The volume of the cube is
(A) 512 m³          (B) 64 m³              (C) 216 m³                   (D) 256 m³          
Solution:

Q9.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
Solution:

Q10.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
Solution:

Q11.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 :

Solution: