JEE MAIN - Mathematics (2015 (Offline) - No. 18)
The number of integers greater than 6,000 that can be formed, using the digits 3, 5, 6, 7 and 8, without repetition, is:
120
72
216
192
설명
For a four digit number the first place can be filled in 3 ways with 6 or 7 or 8 and the remaining four places in 4! ways i.e., 3 $$\times$$ 4! = 72.
For a five digit number it can be arranged in 5! ways,
$$\therefore$$ total number of integers = (72 + 120) = 192.