Witch number produces a rational number when added to 0.5

Any other rational number, since 0.5 is a rational number itself.

For example, 0+0.5=0.5=1/2 = > rational.

1.125+0.5=1 1/8+1/2=1 5/8 = > rational

pi+0.5=3.64159265 ... = > irrational (so pi cannot be added to 0.5 to give a rational number).