5/3 = 1 2/3 for which a decimal approximation is 1.666667

5/2 = 2 1/2 which has an exact decimal representation of 2.5

(1/2 = 5/10)

5/3 is 1 2/3 which has the decimal representation 1.666... (repeating forever)

5/2 is 2 1/2 which has the decimal representation 2.5

I'm not sure what you're asking. Are you asking why dividing by 2 gives a different answer than dividing by 3? Because 2 and 3 are not the same number.