JEE Main 2026 Mathematics question
The number of seven-digit numbers, that can be formed by using the digits 1, 2, 3, 5 and 7 such that each digit is used at least once, is:
Answer: (C)
Solution
The digit multiset is either one digit used 3 times: 5 × 7!/3! = 4200, or two digits used twice: C(5,2) × 7!/(2!2!) = 12600. Total 16800.