Concept:
Probability = Favorable outcomes Total outcomes.
Step 1: Total outcomes.
Each die has 6 outcomes:
\[
6 \times 6 \times 6 = 216
\]
Step 2: Favorable outcomes.
Same number on all dice:
\[
(1,1,1),(2,2,2),\dots,(6,6,6)
\]
Total = 6 outcomes
Step 3: Compute probability.
\[
\frac{6}{216}=\frac{1}{36}
\]