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
