When calculating temperature in Kelvin, which formula is used?

The formula used to convert temperature from Celsius to Kelvin is based on the relationship between the two scales. Kelvin is an absolute temperature scale used in scientific contexts, where 0 K (zero Kelvin) represents absolute zero, the point at which all thermal motion ceases.

Celsius is a scale where 0 °C is defined as the freezing point of water and 100 °C is defined as its boiling point at standard pressure. To convert from Celsius to Kelvin, you need to shift the Celsius temperature up by 273.15, since 0 K is equivalent to -273.15 °C.

In the context of the options presented, rounding off the addition to a whole number gives the simplified formula of adding 273 to the Celsius temperature, which accurately reflects the necessary adjustment. Thus, when calculating temperature in Kelvin, adding 273 to the Celsius temperature correctly produces the desired value in Kelvin for practical use.