How many of the positive integers less than 10000 contain the digit "1" at least once?
by 
MathQuery
ANSWERS: 2
-
You're asking how many 4-digit integers in the range 0001 to 9999 contain the digit 1 at least once. I'd consider a related question: How many of these integers do NOT contain a single digit 1? Each digit may take any of 9 values: 0 or 2-9. Since there are four digits, the total number of such integers is 9^4 = 6561. Thus the answer to the original question is 9999 - 6561 = 3438 numbers with at least one 1.
-
Count those that don't contain it. So You can use 0,2,3,4,5,6,7,8,9, in 4 digit numbers. Hence it's 9^4. . 9^4 - 1, if You exclude 0. . . So now You subtract them from all. ======================= === 99999 - 9^4 + 1 === =======================
RELATED QUESTIONS
Copyright 2023, Wired Ivy, LLC