User blog comment:Wildoneshelper/Guess the number! (Round 1)/@comment-3225604-20140620151453

Let's see why this is solved within 6 attempts:

In 3210, we see two of them are correct in 1, 2, 3 or 0.

In 7654, we see two of them are correct in 4, 5, 6 or 7.

However, 8 and 9 could not be the answers since there are no correct digits.

In 2367, three of them are correct. Therefore, the digit could include 236, 237, 267 or 367.

In 2345, there are only one correct. Therefore, 2 and 3 could not coexist in the digit, which leave only 267 or 367 possible. We also proved that 6 and 7 are the correct numbers.

In 2368, it proves that 2 or 3 could be in one of the right place while we know 6 is in the right place.

In the end, the possible digits are: 0/1, 2/3, 6, 7

Onto green ticks:


 * 2367 2 green ticks
 * 2345 1 green tick
 * 2368 2 green ticks

As we know 6 is in the correct position, we only know that either 2 or 3 are in the wrong place.

Possible answers:

If 2 exists:


 * 2067
 * 2167
 * 2760
 * 2761

If 3 exists:


 * 1367
 * 7360
 * 7361