The three words that have similar meanings are:
1. Impracticable: refers to something that is not possible in practice or is difficult to carry out.
2. Unrealizable: refers to something that cannot be realized or achieved.
3. Preposterous: refers to something that is ridiculous, absurd, or outrageous.
The two words that do not have similar meanings are:
1. Conceivable: refers to something that can be imagined or believed.
2. Viable: refers to something that is feasible, workable, or capable of succeeding.