Question
Quantitative Aptitude Question on Basics of Numbers
Find the number of natural numbers less than (or up to) 1000 having different digits.
Answer
One Digit numbers = 9
Two Digit numbers = 10P2 - 9P1
= 90 - 9
= 81
Three Digit numbers = 10P3 - 9P2
= 720 - 72
= 648
Therefore , Total = 9 + 81 + 648 = 738
So, the answer is 738.