Permutations & Combinations
4-digit numbers in a range without repetition
nta_pyq_2023_jan
Grade None
Question:
The number of numbers, strictly between 5000 and 10000 can be formed using the digits 1, 3, 5, 7, 9 without repetition, is
Step-by-Step Solution
Key Concept: 4-digit numbers between 5000 and 9999 using digits 1,3,5,7,9 without repetition; first digit must be 5, 7, or 9.
First digit: 3 choices (5,7,9). Remaining 3 places from 4 digits: 4$\times$3$\times$2 = 24. Total = 3$\times$24 = 72.
Correct Answer: 4