Question of Exercise 2

Surface Area and Volume of Class 9

Question
The height of a cone is 30 cm. A small cone is cut off at the top by a plane parallel to the base. If its volume be of the volume of the given cone, then the height above the base at which the section has been made, is

Answer

Option 1 10 cm

Option 2 15 cm

Option 3 20 cm

Option 4 25 cm

Frequently Asked Questions

Simplify the following expressions

(√(5) + √(2))2

 

Solution:

Explanation:

 

Simplify

Which of the following rational numbers lies between 0 and - 1

A: 0

B: - 1

C: -1/4

D: 1/4

 

Solution:

Explanation:

0 and 1 cannot be found between 0 and 1.

In addition,0= o/4  and -1= -4/4

We can see that -1/4 is halfway between 0 and -1.

Final Answer:

Hence, the correct option is (c) -1/4

 

Prove that the diagonals of a parallelogram bisect each other

Solution:

Explanation:

We must show that the diagonals of the parallelogram ABCD cross each other.

OA = OC & OB = OD, in other words.

Now AD = BC [opposite sides are equal] in ΔAOD and ΔBOC.

[alternative interior angle] ∠ADO = ∠CBO in ΔAOD and ΔBOC.

Similarly, ∠AOD = ∠BOC by ΔDAO = ΔBCO (ASA rule)

As a result, OA = OC and OB = OB [according to CPCT].

according to CPC

Final Answer:

Hence, it is prove that the diagonals of a parallelogram bisect each other.

 

What is total surface area of sphere

Solution:

Explanation:

  • The radius of the sphere affects the formula for calculating the sphere's surface area. 
  • If the sphere's radius is r and the sphere's surface area is S.
  • The sphere's surface area is therefore stated as Surface Area of Sphere 4πr2, where ‘r’ is the sphere's radius.
  • The surface area of a sphere is expressed in terms of diameter as S=4π(d/2)2, where d is the sphere's diameter.

Final Answer:

Thus, total surface area of sphere is =4πr2.

 

Fill in the blanks If two adjacent angles are supplementary

 they form a __________.

Solution:

Explanation:

  • If the non-common sides of two angles form a straight line, they are called linear pair angles. 
  • The sum of the angles of two linear pairs is  degrees.
  • If the total of two angles is  degrees, they are called supplementary angles.

Final Answer:

A linear pair is formed.

 

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