Question

What are the odds that the last four digits of a social security number are all odd

Answer 1

1/16 or 6.25%

Explanation:

There are 5 even digits and 5 odd digits between 0 and 9.

The probability of a digit being odd is therefore 1/2.

The probability of 4 digits being odd is:

1/2 × 1/2 × 1/2 × 1/2

= (1/2)⁴

= 1/16

= 6.25%