Answer: Charles law states that at a constant pressure, the volume of a fixed mass of dry gas is directly proportional to it's absolute temperature.
Explanation: Let's take volume to be "V" and temperature to be "T".
Therefore, from this definition of charles law, we can say that:
V ∝ T
Since "V" and "T" vary directly, we can equate them by making use of a constant "K".
Therefore, V = KT
Making "K" a factor of the equation, we get: K= V/T.
If the initial volume & temperature are "V1" and "T1" respectively, and the final volume & temperature are "V2" and "T2" respectively; therefore since "K" is a constant,
V1/V2 = T1/T2 = k.
We can therefore generalize the formula as V1/V2 = T1/T2 or
V1*T2 = V2*T1