How many possible combinations does a six-digit iPhone passcode have?

• A. 1,000
• B. 100,000
• C. 1,000,000
• D. 10,000,000

Answer: (C)

Each position in a six-digit numeric passcode can be any digit from 0 to 9, and the choices are independent. Multiply the possibilities for all six positions: 10 × 10 × 10 × 10 × 10 × 10 = 10^6 = 1,000,000. This includes codes like 000000, so there are one million possible passcodes. The other numbers would correspond to codes with a different length (three, five, or seven digits), which isn’t the case here.