Look at several examples of rational numbers in the form 
 (q ≠ 0), where p and q are integers with no common factors other than 1 and having terminating, decimal representations. Can you guess what property q must satisfy?
A rational number 
 is a terminating decimal only, when prime factors of q are 2 and 5 only. Therefore, 
 is a terminating decimal only, when prime factorisation of q must have only powers of 2 or 5 or both.