If $102.7$ is expressed in the form of $p/q$ in lowest form, then $q$ is:

Express $102.7$ as a standard fraction:
$$102.7=\frac{1027}{10}$$
Since 1027 is a prime number and has no common factors with 10, the fraction $\frac{1027}{10}$ is already in its lowest form ($p/q$).Therefore, denominator $q=10$.