find the number of natural number between 100 & 1000 such that at least one of their digit is 6?

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GOOD QUESTION...
IT MEANS BASICALLY WE HAVE TO MAE A THREE DIGIT NUMBER EXCLUDING 100.....WHICH SHOULD CONTAIN 6 AS ITS DIDGIT
WELL THE TOTAL NO. OF WAYS WITHOUT ANY CONSTRAINT IS - 9 X 10 X 10 AS YOU DIDNT MENTION THAT REPITIION IS NOT ALLOWED
TOTAL NO. OF WAYS IN WHICH DIGIT 6 DO NOT COME TOGETHER IS- 
FIRST PLACE CAN BE FILLED WITH 8 WAYS
SECOND PLACE CAN BE FILLED IN 9 WAYS
THIRD PLACE CAN BE FILLED WITH 9 WAYS AGAIN
SO THE REQUIRED ANSWER IS - 900-(649)=251
HENCE THE REQUIRED ANSWER IS 251
NOTE-I SUBTRACTED EXTRA ONE BEACUSE THIS ARRANGEMENT WOULD ALSO HAVE INCLUDED 100 AS ANSWER BUT WE DO NOT NEED 100..SO I DID IT
 
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