Question

A 4-number combination lock uses the digits 1-9 without repetition as follows The second digit is prime. The sum of the third and fourth exceeds 10 The second and fourth digit differ by one The first is 3 greater than the third Exactly one digit is square. What is the combination that will open the lock? Describe fully how you arrived at your answer.

Answer 1

Answer:

Each digit can be 1, 2, 3, 4, 5 and 6.

e.g. 3 | 6 |4 | 2

The fourth digit must be an even number.

How many possible combination are there?

Thank you very much