$36$ students each went to one revision class.  $\dfrac{1}{6}$~of the students went to the physics revision class.  $\dfrac{2}{9}$~of the students went to the biology revision class.  All of the other students went to the chemistry revision class.  How many students went to the chemistry revision class? 
Overseas Competition->Knowledge Point->Word Problem Modules->Solving Problems Involving Fractions and Percentages->Knowing the Base