How many four digit numbers can be formed by the use of digits 1 2 3 4 6 and 7 if one digit is used only once in a number?

Answer 1

To form a four-digit number using the digits 1, 2, 3, 4, 6, and 7 without repeating any digit, we can choose 4 digits out of the 6 available. The number of ways to choose 4 digits from 6 is given by the combination formula ( \binom{6}{4} ), which equals 15. Each selection of 4 digits can be arranged in ( 4! ) (24) different ways. Thus, the total number of four-digit numbers that can be formed is ( 15 \times 24 = 360 ).