By using measuring cylinder.

π x r² = πr²

Area of a square = side \(\times \) side
= 1 m \(\times \) 1 m
= 1 m² or 1 square metre
Area of 10 squares = 1 square metre \(\times \) 10
= 10 square metre

Iron ball sinks in all the liquids apart from mercury.

Density (D) = mass (M) / volume (V).

One astronomical unit is defined as the average distance between the earth and the sun. 1AU = 1.496 x 10¹¹m or 149.6 x 10⁶ m

Density = Mass / Volume
Hence, Volume = Mass / Density
\(=3000 / 8900=30 / 89 \\ =0.34 \mathrm{~m}^{3}\)

Density = Mass / Volume
Hence, Mass = Volume \(\times\) Density
= 125 \(\times\) 7.8 = 975 g.

Physical quantities which can be obtained by multiplying, dividing or by mathematically combining the fundamental quantities are known as derived quantities.
Ex: Area, volume

(i) Place the irregular object on a graph sheet and draw its outline. Then remove the object
(ii) To find the area enclosed by the outline count the number of small squares.
(iii) If more than half-a-square is inside the boundary, count it as one otherwise neglect it.
(iv) The area of each small square is 1sq. mm.
(v) Area of the irregular object = No. of squares x 1 sq.mm.

i) Take a measuring cylinder and pour some water into it.
ii) Note down the volume of water from the readings of the measuring cylinder. Take it as V₁.
iii) Now take a small stone and tie it with a thread.
iv) Immerse the stone inside the water by holding the thread.
v) The stone should not touch the walls of the measuring cylinder.
vi) Note down the volume of water and take it to be V₂
vii) The volume of the stone is equal to the raise in the volume of water.
viii) Volume of stone = V₂ - V₁