Question

Sonji bought a combination lock that opens with a four-digit number created using the digits 0 through 9. The same digit cannot be used more than once in the combination.

If Sonji wants the last digit to be a 7 and the order of the digits matters, how many ways can the remaining digits be chosen?

Answer 1

B. 504

Explanation:

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Answer 2

504 ways

Explanation:

We know that since Sonji wants the last digit to be 7 and that numbers don't repeat, there are only 9 possibilities for the first digit, 8 possibilities for the second digit, 7 possibilities for the third digit, and 1 possibility for the fourth digit (which is 7).

Using the Fundamental Counting Principle, there are 9*8*7*1 = 504 ways for the remaining digits to be chosen.