Question

How many numbers less than 1000 can be made from the digits 1, 2, 3, 4, 5, 6 (repetition is not allowed).

• A. 156
• B. 160
• C. 150
• D. None of these

Answer 1

Answer: (A)

156

Answer 2

Number of 1 digit numbers $=^{6} ⥂ P_{1}$

Number of 2 digit numbers $=^{6}P_{2}$

Number of 3 digit numbers $=^{6} ⥂ P_{3}$

The required number of numbers $= 6 + 30 + 120 = 156$.