Question

is 0.3 the multiplicative inverse of $3 \frac{1}{3}$

Answer 1

3/10 Yes, its correct.

Answer 2

3 1/3 is nothing but 10/3
To find multiplicative inverse :
consider the multiplicative inverse to be x 
10/3 * x = 1
x is 3/10
3/10 is 0.3