Use the Permutations Formula
-A combination lock has 20 numbers on it. How many different 3-digit lock combinations are possible if no digit can be repeated?
A) 6840
B) 2280
C) 1140
D) 380

Question

Quizplus · Accepted Answer

The number of different 3-digit lock combinations possible without repeating any digit can be calculated using the permutations formula, which is n! / (n - r)!, where n is the total number of options (20 numbers) and r is the number of selections to make (3 digits). So, it's 20! / (20 - 3)! = 20! / 17! = 20 x 19 x 18 = 6840.