Question

basic concepts of surface area and area and volume of class 9th cbsc

Answer 1

the basic concept of surface area and volume are

1) the surface area of cube is 6 $a^2$ and we can say that we have to multiply every multiple for example to get an area of four side we have to multiply 4 × $a^2$

2) the area of a cuboid of a surface area we can see that the formula are very important at that time.

3) for taking all the volume we have to properly learn the formulas and something other that is very important at that time is that we always have to think about the diameter if the diameter is multiple of 7 then we have to take as diameter of onto so that it would get easy to multiply for example if the diameter is 21 so we don't take 10.5 we have to take as the following equation

$\frac{22}{7}×(\frac{21}{2})^2×h$

4) the area of cone is one third of area of the cuboid and four third of that cylinder.

Answer 2

Answer:

basics

Step-by-step explanation:

CUBOID

Let length = l, breadth = b and height = h units. Then

Volume = (l x b x h) cubic units.

Surface area = 2(lb + bh + lh) sq. units.

Diagonal = l2 + b2 + h2 units.

CUBE

Let each edge of a cube be of length a. Then,

Volume = a3 cubic units.

Surface area = 6a2 sq. units.

Diagonal = 3a units.

CYLINDER

Let radius of base = r and Height (or length) = h. Then,

Volume = (r2h) cubic units.

Curved surface area = (2rh) sq. units.

Total surface area = 2r(h + r) sq. units.

CONE

Let radius of base = r and Height = h. Then,

Slant height, l = h2 + r2 units.

Volume = r2h cubic units.

Curved surface area = (rl) sq. units.

Total surface area = (rl + r2) sq. units.

SPHERE

Let the radius of the sphere be r. Then,

Volume = r3 cubic units.

Surface area = (4r2) sq. units.

HEMISPHERE

Let the radius of a hemisphere be r. Then,

Volume = r3 cubic units.

Curved surface area = (2r2) sq. units.

Total surface area = (3r2) sq. units.

Note: 1 litre = 1000 cm3.