How many 4-digit numbers can be formed using the digits 0, 1, 2, 3, 4, 5, 6, if repetitions are not allowed?
A) 23
B) 2401
C) 24
D) 840

Question

Quizplus · Accepted Answer

For a 4-digit number, the first digit can be any of the 6 options (1-6, since 0 cannot be the first digit), the second digit can be any of the remaining 6 (including 0 this time), the third digit can be any of the remaining 5, and the fourth digit can be any of the remaining 4. Therefore, the total number of combinations is 6 * 6 * 5 * 4 = 720.

How Many 4-Digit Numbers Can Be Formed Using the Digits