A security alarm requires a four-digit code. The code can use the digits 0–9 and the digits cannot be repeated.What is the approximate probability that the code only contains odd numbers?

There are 10 × 9 × 8 × 7 = 5,040 possible four-digit codes, since digits cannot repeat. For a code to contain only odd digits, each digit must come from 1, 3, 5, 7, or 9, giving 5 × 4 × 3 × 2 = 120 codes. The probability is 120 ÷ 5,040 ≈ 0.02381, so the answer is D, 0.02381.

AI-written and checked against the verified answer.