0
Since the repetition of digits is not allowed then the number of 7 digit numbers formed = 9 x 9 x 8 x 7 x 6 x 5 x 4 = 544320
Explanation:
The first digit of the number can't be 0 so we have 9 digits to choose from.
And the remaining last places(here 6) can be filled by using the remaining 9 digits i.e. 9P6 = 9!/(9-6)! = 9 x 8 x 7 x 6 x 5 x 4
So, the result is 9 x 9P6 .
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How many sets of 3 numbers can be made out of 12 different numbers?
You can select 12 numbers for the first digit, 11 numbers for the second digit, and 10 numbers for the third digit; so 12*11*10 = 1320 sets of 3 numbers can be made out of 12 different numbers.
How many different 3 digit house numbers could be made using numerals 4 7 8?
Six.
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210
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How many numbers can you make from 650271 without repeating a digit?
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