Class activity used fraction circle pieces and students discovered that 2 pieces must be at least 1/2 to make a whole. Using only 2 pieces if each is less than 1/2 you will never get 1 whole.
The same holds true for 1/2. You must have 2 pieces that are at least 1/4 to make 1/2.

Students modeled the fractions for the even numbered word problems and used the reasoning to estimate the answer between halves (0, 1/2, 1, 1-1/2, 2...)