Solve.
-How many different three-number "combinations" are possible on a combination lock having 21 numbers on its dial?
A) 15,120
B) 7560
C) 3990
D) 7980

Question

Quizplus · Accepted Answer

The number of different three-number combinations is calculated by 21^3, as each number in the combination can be any of the 21 numbers. Thus, 21 * 21 * 21 = 9261. However, since the problem asks for "combinations" and not "permutations," we need to divide by the number of ways to arrange 3 numbers (3!), which is 6. So, 9261 / 6 = 1543.5, which is not an integer, indicating a misunderstanding in the problem's context. Assuming the problem meant permutations, the correct calculation would be 21 * 20 * 19 = 7980, which matches option D.

Solve. -How Many Different Three-Number "Combinations" Are Possible on a Combination