The experimental probability of an event is calculated using the formula:
\[ \text{Experimental Probability} = \frac{\text{Number of successful outcomes}}{\text{Total number of trials}} \]
In this case, the number of times the cube landed on 3 is 10, and the total number of rolls is 30. Therefore, the experimental probability of landing on a 3 is:
\[ \text{Experimental Probability of 3} = \frac{10}{30} \]
To simplify the fraction \(\frac{10}{30}\), we can divide both the numerator and the denominator by their greatest common divisor, which is 10:
\[ \frac{10 \div 10}{30 \div 10} = \frac{1}{3} \]
Thus, the experimental probability of landing on a 3 is:
\[ \boxed{\frac{1}{3}} \]