Question

How many 3 digit number can.Be.Formed using the.Digits.0,1,2,3,4,5,6,7,8,9 if repetitionis.Not allowed?

Answer 1

102 , 210 , 789 , 764 , and many more...

Answer 2

Every three digit numbers contain three places - ones place, tens place and hundreds place. Here it is the exception that the hundreds place can't accept the value 0 else the number will be of two digit.

Here repetition is not allowed too. So,

• hundreds place can accept any of the 9 numbers from 1 to 9.
• once hundreds place is filled, the tens can be filled by any of the 9 possible numbers among 0 and 9.
• the ones place can be filled by any of the 8 numbers among them, since two digits are used.

Hence the required no. of three digit numbers is 9 × 9 × 8 = 648.

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