To calculate the experimental probability of landing on a 3 when rolling a six-sided number cube, you use the formula for experimental probability:
\[ P(\text{Event}) = \frac{\text{Number of times the event occurs}}{\text{Total number of trials}} \]
In this case, the number of times the event (landing on a 3) occurs is 10, and the total number of trials (rolls of the number cube) is 30.
So, the probability \( P(3) \) is given by:
\[ P(3) = \frac{10}{30} \]
Next, we simplify the fraction:
\[ P(3) = \frac{10 \div 10}{30 \div 10} = \frac{1}{3} \]
Thus, the experimental probability of landing on a 3 is:
\[ P(3) = \frac{1}{3} \]