Math Problem Statement
Solution
Let's solve the problem step by step.
Problem:
We need to determine how many 4-digit numbers can be formed using the digits without repetition such that the numbers are divisible by 5.
Key Concepts:
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Divisibility by 5: A number is divisible by 5 if its last digit is either or . In this case, since is not in the set of digits, the last digit must be 5.
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Formation of 4-digit numbers:
- Since the last digit is fixed as , we are left with the digits to arrange in the first three places.
- These remaining digits can be arranged in different orders to form valid numbers.
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Permutation Calculation:
- The number of ways to arrange distinct objects is given by (factorial of ).
- Here, we have digits (excluding ) to arrange in positions, so the number of arrangements is .
Solution:
- Fix as the last digit.
- Arrange the remaining digits () in the first positions:
Thus, there are 24 such numbers.
Final Answer:
The correct option is: (1) 24
Would you like a detailed explanation of permutations or help with similar problems? Here are some related questions to expand on:
- How many 4-digit numbers can be formed using the same digits if repetition is allowed?
- How many 4-digit numbers divisible by can be formed from the digits ?
- How many 5-digit numbers can be formed without repetition using these digits?
- How does the condition of divisibility by change if is included in the digits?
- How many numbers are divisible by when formed using these digits?
Tip: Always identify constraints (like divisibility rules or digit repetition) before solving permutation problems.
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Math Problem Analysis
Mathematical Concepts
Divisibility rules
Permutations
Factorials
Formulas
n! = n × (n-1) × (n-2) × ... × 1
Divisibility rule for 5: A number is divisible by 5 if its last digit is 0 or 5
Theorems
Fundamental Counting Principle
Permutation Theorem
Suitable Grade Level
Grades 8-10
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