Q. How many numbers lying between 10 and 1000 can be formed from the digits 1, 2, 3, 4, 5, 6, 7, 8, 9 (repetition of digits is allowed)?
A) 1024
B) 810
C) 2346
D) None of these
Explanation
(b)
Case I When number in two digits.
Total number of ways$= 9 \times 9 = 81$
Case II When number in three digits
Total number of ways $= 9 \times 9 \times 9 = 729$
$\therefore$ Total number of ways $= 81 + 729 = 810$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.