The probability of rolling doubles on a single turn is the number of favorable cases over the number of total cases, the favorable cases are those when you get a double, the number of total cases is the number of total possible outcomes.
Now, the number of total possible outcomes is
The number of favorable cases is
Therefore, the probability of rolling doubles is:
Now, the probability of rolling double 3 times in succession is the product of rolling a double in a single turn, therefore:
Answer:
The probability of rolling doubles on a single turn is:
The probability of rolling doubles 3 times in succession is: