Courses

# Very Short Answers Type Questions- Surface Areas and Volumes Class 9 Notes | EduRev

## Class 9 : Very Short Answers Type Questions- Surface Areas and Volumes Class 9 Notes | EduRev

The document Very Short Answers Type Questions- Surface Areas and Volumes Class 9 Notes | EduRev is a part of the Class 9 Course Mathematics (Maths) Class 9.
All you need of Class 9 at this link: Class 9

Question 1. What is the longest pole that can be put in a room of dimensions l = 10 cm, b = 10 cm and h = 5 cm?
Solution:
The longest diagonal of a cuboid =

âˆ´ The length  of the required pole (diagonal) =

Question 2. Total surface area of a cube is 96 cm2. What is its volume?
Solution:
Total surface area of the cube = 6l2

âˆ´

Thus, the volume of the cube = l3 = 43 = 64 cm

Question 3. The radius of a sphere doubled. What per cent of its volume is increased?
Solution:
Original volume = (4/3)Ï€r3

Increased volume = (4/3)Ï€(2r)3 = 32/3Ï€r3

Increase in volume =  32/3Ï€r3 -  4/3Ï€r3 = 28/3Ï€r3

âˆ´ Per cent increase in volume =

Question 4. Write â€˜True or Falseâ€™ for the following statements: (i) A right circular cylinder just encloses a sphere of radius r as shown in the figure. The area of the sphere is equal to the curved surface area of the cylinder.
Solution:
True.

âˆµ [Radius of the sphere] = [Radius of the cylinder] = r

âˆ´ Diameter of the sphere = 2r
â‡’ Height of the cylinder (h) = 2r
Now, surface area of the sphere = 4Ï€r
And curved surface area of the cylinder = 2Ï€rh = 2Ï€r (2r) = 4Ï€r2

(ii) An edge of a cube measures â€˜râ€™ cm. If the largest possible right circular cone is cut out of this cube, then the volume of the cone (in cm3) is 1/6Ï€r3
Solution: False.
âˆµ Height of the cone = r cm
âˆ´ Diameter of the base of the cone = r cm

â‡’ Radius of the base of the cone = (r/2) cm

Now volume of the cone

Question 5. If the total surface area of a sphere is 154 cm2. Find its total volume.
Solution:
Let â€˜râ€™ be radius of the sphere
âˆ´ Total S.A. = 4 Ï€ r2 = 154 cm2

or

Now,

Question 6. If the radius of a sphere is 3r then what is its volume?
Solution:

Offer running on EduRev: Apply code STAYHOME200 to get INR 200 off on our premium plan EduRev Infinity!

## Mathematics (Maths) Class 9

190 videos|233 docs|82 tests

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

;