Why we use 180/100 or 100/180 in the conversion of F and C degree?

The conversion factor of 180/100 or 100/180 is used in the conversion of Fahrenheit (F) and Celsius (C) degrees because the two temperature scales have different starting points and different intervals between each degree.

To convert from Fahrenheit to Celsius, you subtract 32 from the Fahrenheit temperature and then multiply by 5/9. This is because the Fahrenheit scale has a starting point of 32 degrees (the freezing point of water) and each degree is 5/9 of a Celsius degree.

To convert from Celsius to Fahrenheit, you multiply the Celsius temperature by 9/5 and then add 32. This is because the Celsius scale has a starting point of 0 degrees (the freezing point of water) and each degree is 9/5 of a Fahrenheit degree.

So, the conversion factor of 180/100 or 100/180 is used to account for the different starting points and intervals between the two temperature scales.

The conversion formulas between Fahrenheit (°F) and Celsius (°C) do not involve the numbers 180 or 100. They are as follows:

°C to °F:

```
°F = (°C × 9/5) + 32
```

°F to °C:

```
°C = (°F - 32) × 5/9
```