Answer :
The number of combination possible = 15625
When the numbers are repeating
The number of possible combinations = 13800
Given that a certain combination lock requires three selections of numbers
Total possible numbers = 25
Part a
Total number of combinations possible = 25 × 25 × 25
Multiply the numbers
= 15625 possible combinations
Part b
The given condition is no number may be used twice
Total number of combinations possible = 25 × 24 × 23
Multiply the numbers
= 13800 possible combinations
Therefore, when the number are repeating, the possible combinations are 15625 and when the numbers are not repeating the possible combinations are 13800
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