Question

Let X₁ X₂ X₃ X₄ X₅ X₆ be a six digit number such that 0 < X₁ < X₂ < X₃ < X₄ < X₅ < X6. If these six digits. numbers are arranged in ascending order, then the number at 72^th position is ____.

Answer 1

Number of numbers starting with 1 = ⁸C₅ = 56

Number of numbers starting with 23 = ⁶C₄ = 15

Next number at 72^nd position is 245678.