Relativistic mean proportion

The so called modern physics is at present included in the curricula of high school.Therefore, we often organize in-depth lessons on quantum mechanics and on the special theory LIP SHINE SMOOCH of relativity (SR).In the following sections, we want to show a lesson given by the first author of this paper.He proposes to students a proportion to deduce Lingerie-premium relativistic time dilation and length contraction without knowing the Lorentz transformations.