JEE Main 2019 Mathematics question
The number of natural numbers less than 7,000 which can be formed by using the digits 0, 1, 3, 7, 9 (repetition of digits allowed) is equal to:
Answer: (D)
Solution
1-digit 4, 2-digit 20, 3-digit 100, 4-digit (first digit 1 or 3) 250: total 374.