Question:easy

How many numbers between \(10\) and \(10,000\) can be formed by using the digits \(1,2,3,4,5\), if no digit is repeated in any number?

Show Hint

When numbers are to be formed within a range, first identify the possible number of digits, then count each case separately using permutations.
Updated On: Jun 26, 2026
  • \(200\)
  • \(775\)
  • \(60\)
  • \(120\)
Show Solution

The Correct Option is A

Solution and Explanation

Step 1: Understand the problem scope.
We need to count all numbers strictly between 10 and 10000 formed from digits $\{1,2,3,4,5\}$ with no repetition. Numbers in this range are 2-digit, 3-digit, and 4-digit numbers. Since no digit is 0, there is no restriction on the leading digit.
Step 2: Count 2-digit numbers.
Choose and arrange 2 digits from 5 available digits (order matters, no repetition). This is the permutation ${}^5P_2 = 5 \times 4 = 20$.
Step 3: Count 3-digit numbers.
Choose and arrange 3 digits from 5 available digits. This is ${}^5P_3 = 5 \times 4 \times 3 = 60$.
Step 4: Count 4-digit numbers.
Choose and arrange 4 digits from 5 available digits. This is ${}^5P_4 = 5 \times 4 \times 3 \times 2 = 120$.
Step 5: Why not 5-digit numbers?
The upper bound is 10000 (exclusive). A 5-digit number formed from $\{1,2,3,4,5\}$ would be at least 12345, which exceeds 10000, so no 5-digit numbers qualify.
Step 6: Add all cases.
Total = $20 + 60 + 120 = 200$.
\[ \boxed{200} \]
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