How many 5-digit numbers can be formed using the digits 0, 1, 2, 3, 4, 5, 6, if repetition of digits is not allowed? a.119 b.16,807 c.2520 d.120

c. 2520

Explanation:
Repetition is not allowed, therefore:
1st digit can be any of the given 7 numbers
2nd digit can be any of the remaining 6 numbers
3rd digit can be any of the remaining 5 numbers
4th digit can be any of the remaining 4 numbers
5th digit can be any of the remaining 3 numbers
This means that:
number of possible combinations = 7 * 6 * 5 * 4 * 3 = 2520 numbers

Hope this helps :)

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