Three hens and four rabbits are in a cage. How many legs do they have?~(adapted from $$2011$$ Math kangaroo Problems, Level $$1-2$$, Question \#$$4$$) 
Overseas Competition->Knowledge Point->Word Problem Modules->Unitary Method Problems->Finding the Total Value using Unitary Method
A hen has two legs and a rabbit has four legs, so three hens have six legs and four chickens have sixteen legs.  $6+16=22$ 