Question

A passcode on a smartphone consists of 4 ​digits, and repetition of digits is allowed.

​a) Determine the number of possible four​-digit passcodes.
​b) If a person finds a smartphone and randomly enters 4 ​digits, what is the probability that the correct passcode is​ entered?

Answer 1

a) 10 x 10 x 10 x 10= 10000 possible four digit passcodes. We are multiplying by 10 each time because there are 10 digits (0-9) and repetition is allowed.

b) 1/10000 chance since each passcode is different!