Charles' Law
Now we know: `(P_1\ \ V_1)/T_1=(P_2\ \ V_2)/T_2`
and we know Charles' law `=` Pressure constant
If we choose ONE for the value of `P`
NOTE: It doesn't really matter what value you choose, they will cancel each other out being the same
then `(1xxV_1)/T_1=(1xxV_2)/T_2`
is the same as
`V_1/T_1=V_2/T_2`
This is Charles' law