JEE Main 2014 Mathematics question
An eight digit number divisible by 9 is to be formed using digits from 0 to 9 without repeating the digits. The number of ways in which this can be done is:
Answer: (4)
Solution
The ten digits sum to 45, so the two omitted digits must sum to a multiple of 9, i.e. to 9: the pairs are (0,9), (1,8), (2,7), (3,6), (4,5) — five pairs. If (0,9) is omitted, none of the
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