I found an answer from worldbuilding.stackexchange.com

**I**'m stranded on an alien planet. How **do I measure** an earth year ...

**Use** a stick to **create** a sundial. Now start counting your heartbeats. Very roughly
**you can** expect ~5,000 per hour (80 BPM). **Make** marks where the shadows lie ...

For more information, see **I**'m stranded on an alien planet. How **do I measure** an earth year ...

I found an answer from infolab.stanford.edu

4 Combinatorics and Probability

combinatorics. The **concepts** that surround **attempts** to **measure** the likelihood of
... problem is counting the **number** of anagrams of a word that may **have** some ...
Probabilistic reasoning and **ways** that **we can estimate** probabilities of com- ...
thus the **number** of **possible** outcomes of the sort will be **equal** to Π(n), the
**number**.

For more information, see 4 Combinatorics and Probability

I found an answer from phys.libretexts.org

1.3: Accuracy, **Precision**, and Significant Figures - **Physics** LibreTexts

Oct 25, 2020 **...** You **measure** the **length** of the paper three times and obtain the ... Usually an
object with unknown **mass** is placed in one pan and ... This indicates a low
**precision**, high accuracy **measuring** system. ... is an uncertainty in anything
calculated from **measured** quantities. ... 1.2: **Physical Quantities** and **Units**.

For more information, see 1.3: Accuracy, **Precision**, and Significant Figures - **Physics** LibreTexts

Like the precise measurements in science are required, reasonable approximations of physical quantities using rudimentary ideas and general observations are equally valuable.

a) \text{ Density } = \frac{\text{ mass }}{\text{ volume }}

Total mass of rain fall can be determined with knowledge of rainfall volume and water density.

Density of water = 10^{3} kgm^{-3}

During the monsoon, the height of the water is measured h = 215 cm = 2.15 m

Area of the earth A = 3.3 * 10^{12} m^2

Volume of the rain fall = Ah = 3.3 * 10^{12} m^2 * 2.15 m

= 7.1 * 10^{12} m^3

Total mass of rain fall = \text{ Density * volume } = 10^{3} kgm^{-3} * 7.1 * 10^{12} m^3

= 7.1 * 10^{15} kg

b)We can estimate the mass of the elephant mass using the Archimedes principle

As per the Archimedes principle, the upward buoyant force exerted on a body immersed in a fluid, whether partially or completely submerged, is equivalent to the weight of the fluid that the body displaces.

Displaced water mass =(displaced water volume)x (density of water)

When elephant is immersed in water, measure the volume of water displaced = V

Displaced water mass = V *10^{3} kgm^{-3}

Mass of water = Mass of object

hence, estimated mass of the elephant = V *10^{3} kgm^{-3}

c) To measure the wind speed a rotating device( anemometer) can be used. When the wind blows, wind speed is given by the number of rotations per second.

d) Area of the head surface = A

Measure the radius of the hair using the screw gauge = r

Area of the hair a = \pi r^2

The number of hair strands = \frac{\text{ Area of the head surface }}{\text{ Area of the hair }}

= \frac{A}{a} = \frac{A}{\pi r^2}

e) Calculating the number of molecules of air in the classroom

Volume of the class room V_c = lbh where, l -length, b-breadth and h - height

Volume of the air molecule(sphere in shape) V_a = \frac{4}{3} \pi r^3 where, r- radius of the air molecule

Number of molecules of air = \frac{V_a}{V_c}

= \frac{ \frac{4}{3} \pi r^3 }{lbh}

= \frac{4 \pi r^3 }{3 * lbh}

Hence, number of molecules of air in the classroom = \frac{4 \pi r^3 }{3 * lbh}