Math Problem Statement
Solution
To solve this question, let’s break it into steps based on the given problem and solution:
Question Recap:
We are tasked to find how many five-digit numbers are possible if the number is greater than 40,000 and digits cannot be repeated.
Step-by-Step Solution:
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Analyze the first digit:
- To ensure the number is greater than 40,000, the first digit (most significant) must be 4, 5, 6, 7, 8, or 9. That gives 6 options.
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Second digit selection:
- Once the first digit is chosen, we have 9 remaining digits to pick from (since repetition is not allowed). This gives 9 options for the second digit.
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Third digit selection:
- After selecting the first and second digits, 8 digits remain to choose from, so there are 8 options for the third digit.
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Fourth digit selection:
- Now, 7 digits remain, providing 7 options for the fourth digit.
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Fifth digit selection:
- Finally, 6 digits remain, so there are 6 options for the fifth digit.
Total Calculation:
The total number of five-digit numbers is:
This matches the solution provided in the image.
Final Answer:
There are 2,160 five-digit numbers greater than 40,000 where digits cannot be repeated.
Let me know if you'd like further clarification or additional examples.
Here are 5 related questions for practice:
- How many five-digit numbers less than 50,000 can be formed without repeating digits?
- What is the total number of five-digit numbers possible without repeating digits?
- How many six-digit numbers greater than 100,000 can be formed without repeating digits?
- What happens to the count if the restriction of non-repeating digits is removed?
- How many numbers greater than 40,000 can be formed if only odd digits are allowed?
Tip: Always identify and limit the options for the most restrictive digit(s) first when solving digit-based problems.
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Math Problem Analysis
Mathematical Concepts
Permutations
Number theory
Counting principles
Formulas
Total combinations = product of choices for each digit
Theorems
Basic principles of permutations and combinations
Suitable Grade Level
Grades 8-10
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