Asked by sashank2 | 28th Feb, 2010, 03:00: PM
At least 2 digits should be identical, which means we'll not have any 4 digit numbers with distinct digits.
Divisible by 5 requires the units digit of the 4 digit number to be fixed at 5.
Now we have to select THREE more digits, to select each out of the three we have 5 different choices, 1,2,3,4 and 5, as the digits can be repeated.
Hence the total number of ways = 5x5x5 = 125.
Now the 4 digit numbers with distinct digits, no repeatations, so the selection of three digits, we have only 1,2,3 and 4 available.
First digits can be selected in 4 ways,
Second in 3 ways,
Third in 2 ways.
Total number of distinct digits, 4x3x2 = 24.
So the required 4 digit numbers, 125-24 = 101.
Answered by | 28th Feb, 2010, 07:20: PM
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