A physical quantity is something that can be measured. Scalar quantities only have a magnitude or size.
Some examples of scalar quantities include:
The sum of scalar quantities can be found by adding their values together.
Calculate the total mass of a 75 kg climber carrying a 15 kg backpack.
75 kg + 15 kg = 90 kg
Scalar quantities can be subtracted by subtracting one value from another.
A room is heated from 12°C to 21°C using a radiator. Calculate the increase in temperature.
21°C - 12°C = 9°C