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There are 900 3-digit numbers, 100 to 999.
The 3 may be in the hundreds place, the tens place, or the ones.
The numbers 300 - 399 have 3 in the hundreds place.
The numbers 130, 131 ... 938, 939 have 3 in the tens place.
The numbers 103, 113, 123 ... 993 have 3 in the ones place.
That would total 100 + 90 + 90 = 280 except that now we have double counted some numbers with 2 or more threes in them. I believe if you count carefully you will find 19 double counted numbers in the 300 - 399 group and 8 numbers with the tens digit and ones digit equal to 3. Lastly, the number 333 was triple counted. 280 - 28 = 252. There are several ways to solve this problem. I encourage you to double-check my results ... who is to say this is correct?
What else can I help you with?
How many three digit numbers have odd prime number as 1st digit A prime number as 2nd digit and an odd number as 3rd digit?
There are 17 such numbers.
How many 3 digit numbers contain the digit 2 at least once?
252
How many 3 digit numbers are there that contain at least 1 seven?
252
How many 3-digit numbers are there using 2 4 6 8 and 9?
There are 5 numbers which can make the 3 digit numbers in this example. Therefore each digit in the 3 digit number has 5 choices of which number can be placed there. Therefore number of 3 digit numbers = 5 x 5 x 5 = 125
How many numbers does a creditcard number have?
A credit card number is a 16 digit number.
