Find the odd man out : 187, 264, 386, 473, 682, 781

Concept:

In a numeric "find the odd one out" set, look for a digit relationship that holds for every number except one; the number that breaks the shared rule is the odd one out.

Applying it here:

Check whether the middle digit of each three-digit number equals the sum of its two outer digits:

1. 187: middle digit is 8; outer digits 1 and 7 sum to 8, so it matches the pattern.

2. 264: middle digit is 6; outer digits 2 and 4 sum to 6, so it matches the pattern.

3. 386: middle digit is 8; outer digits 3 and 6 sum to 9, so it does not match the pattern.

4. 473: middle digit is 7; outer digits 4 and 3 sum to 7, so it matches the pattern.

5. 682: middle digit is 8; outer digits 6 and 2 sum to 8, so it matches the pattern.

6. 781: middle digit is 8; outer digits 7 and 1 sum to 8, so it matches the pattern.

Cross-check:

Five of the six numbers strictly satisfy "middle digit = sum of outer digits"; only one number breaks the rule, confirming it as the unique exception.

Result: the odd number out among the given options is 386.