The number of five digit numbers that can be formed by using digits 1, 2, 3 only, such that three digits of the formed number are identical, is

When exactly three digits are identical and the remaining two are different, then the number of such numbers 3C15!3!=60When three digits are identical and the remaining two are also identical, then the number of ways= 3C2(2)5!3!2!=60Thus, the number of such numbers = 120.