Correct Option
To form a four-digit number less than 2000 using the digits 1, 2, 3, and 4 without repetition, the thousands digit must be 1. Any other digit (2, 3, or 4) in the thousands place would result in a number equal to or greater than 2000.
With 1 fixed in the thousands place, the remaining three digits (2, 3, 4) can be arranged in the hundreds, tens, and units places. The number of permutations of these three digits is 3! = 3 × 2 × 1 = 6.
The six possible numbers are:
- 1234
- 1243
- 1324
- 1342
- 1423
- 1432
The sum of these numbers is: 1234 + 1243 + 1324 + 1342 + 1423 + 1432 = 7998.
Incorrect Options
Options 2, 3, and 4 are incorrect as they do not represent the sum of all four-digit numbers less than 2000 formed by the digits 1, 2, 3, and 4 without repetition, as calculated above.