How many 7 digit numbers can be formed using the digits 1, 2, 0, 2, 4, 2, 4?
A) 120 B) 360
C) 240 D) 424
Answer: B) 360
Explanation:
There are 7 digits 1, 2, 0, 2, 4, 2, 4 in which 2 occurs 3 times, 4 occurs 2 times.
Number of 7 digit numbers = 7!3!×2! = 420
But out of these 420 numbers, there are some numbers which begin with ‘0’ and they are not 7-digit numbers. The number of such numbers beginning with ‘0’.
=6!3!×2! = 60
Hence the required number of 7 digits numbers = 420 – 60 = 360
7 digit number combinations
