A combination lock has a code consisting of 3 numbers, each of which can be 0 to 39, with numbers repeated. Jillian says that there are only 120 possible codes. Is Jillian correct? If not, explain her error.

Answer:

No, Jillian is not correct. According to the fundamental counting principle, the total number of possible codes would be (40)(40)(40) 64,000. Jillian multiplied by 3 instead of multiplying the number of possibilities for each digit.