The number of 4-digit numbers that can be made with the digits 1, 2, 3, 4
MATHEMATICS · Single correct · AoPS · Mathematics · Follow the Rules · Follow the Rules
Problem
The number of 4-digit numbers that can be made with the digits 1, 2, 3, 4, and 5, in which at least two digits are identical, is
(1) 45−51
(2) 505
(3) 600
(4) 120