Answer:
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504 ways.
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Step-by-step explanation:
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Easier Explanation:
The answer is 504 because if we are looking for 3 numbers that matter the order, it would be permutation, so, 9 times 8 times 7 is 504.
Advanced Explanation:
The total Combinations from 0-9 digits: {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
Let the four digit number be W, X, Y, Z
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W has 9 combinations because 7 is the last digit we omit it,then 9 combinations are left
X has 8 combinations because 7 is the last digit and the repetition of numbers is not allowed, so we remove 7 and W.
Y has 7 combinations because 7, W and X are omitted.
Z has 1 combination because last digit must be 7.
So, total number of ways (n), can be calculated as:
n= 9*8*7*1 = 504.
n= 504.
If you have any questions, feel free to comment below.
Best of Luck to you.
Merry Christmas!
