Answer:
Linear mass density,

Step-by-step explanation:
Given that,
Mass of the string, m = 0.3 g = 0.0003 kg
Length of the string, l = 1.5 m
The linear mass density of a string is defined as the mass of the string per unit length. Mathematically, it is given by :



or

So, the linear mass density of a string is
. Hence, this is the required solution.