If a lock requires 3 different digits from 0 to 9, how many different combinatio

Practice Questions

Q1
If a lock requires 3 different digits from 0 to 9, how many different combinations can be formed?
  1. 720
  2. 1000
  3. 900
  4. 120

Questions & Step-by-Step Solutions

If a lock requires 3 different digits from 0 to 9, how many different combinations can be formed?
  • Step 1: Understand that we need to choose 3 different digits from the numbers 0 to 9. This means we have 10 possible digits to choose from.
  • Step 2: Recognize that the order in which we choose the digits matters because they will form a combination for the lock.
  • Step 3: Use the formula for permutations to find the number of ways to arrange 3 digits out of 10. The formula is nPr = n! / (n - r)!, where n is the total number of items to choose from, and r is the number of items to choose.
  • Step 4: In our case, n = 10 (the digits 0 to 9) and r = 3 (the digits we want to choose). So we calculate 10P3.
  • Step 5: Calculate 10P3: 10! / (10 - 3)! = 10! / 7! = (10 × 9 × 8) = 720.
  • Step 6: Conclude that there are 720 different combinations of 3 different digits that can be formed.
  • Permutations – The question tests the understanding of permutations, specifically how to calculate the number of ways to arrange a subset of items from a larger set.
  • Combinatorial Counting – It also involves combinatorial counting principles, where the order of selection matters since the digits are used in a lock combination.
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