Question

A padlock has a 4 digit key code
2657 - has two correct digits but neither are in the correct place
0415 - Has one correct digit but it's in the wrong place
4268 - Has no correct digits
1749 - Has two correct digits, both in the correct place.
All the 4 digits in the key are different.
`what is the code for the padlock?

Answer 1

As 4268 has no correct numbers, delete these from the other combinations given.

In 2657, 2 and 6 get cancelled, leaving only 5 and 7. Thus, 5 and 7 are the two numbers in the incorrect places.
In 0415, 4 gets cancelled. As there is only one correct number here and we know 5 is a correct number from the previous combination, 5 is the number in the incorrect position.
So, 5 is in either of the first two places.
In 1749, we know 4 is cancelled and 7 is a correct number. 1 can't be a correct number because in 0415 there is only one correct number. Thus, the correct numbers in the correct places are 7 and 9.
So _7_9. As 5 is in either of the first two places, it now has to be the first number.
Thus, 57_9. As all the digits are different and 8 is not a part of the number, the missing number is 3.

So the number is 5739.

Answer 2

Answer:

Why not 5779?

Explanation:

There isn't any 3 in the given clue.

Assuming we take only what is given. 7 will fulfil its criteria in both places.