In a certain country, 10-digit telephone numbers with the following format were introduced: Format Number of digits Area Code 3 digits Exchange Code 3 digits Number 4 digits Example 901 544 1230 Digits may be repeated - NSC Mathematics - Question 10 - 2020 - Paper 1

Applying the given restrictions:

• Area Code: The first digit can be 2-9 (8 options), and the next two can be 0-9 (10 options each). Thus total combinations = $8 \times 10^2$.
• Exchange Code: The first digit can be 2-9 (8 options) and the second can be 2-9 (8 options), while the third can be 0-9 (10 options). Thus total combinations = $8 \times 8 \times 10$.
• Number: The first digit must be 0 or 1 (2 options), and the other three can be 0-9 (10 options each). Thus total combinations = $2 \times 10^3$.

Total valid numbers = $(8 \times 10^2) \times (8 \times 8 \times 10) \times (2 \times 10^3) = 1,024 \times 10^9$.

To determine the probability, we divide the number of valid phone numbers by the total possible phone numbers:

Probability = ( \frac{1,024 \times 10^9}{10^{10}} = \frac{64}{625} \approx 10.24% ).