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Deleted - just one question per post thanks.

 

3) How many positive integers less than 1000 have at least one digit of 0?

 May 25, 2019
edited by Melody  May 26, 2019
 #1
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3) How many positive integers less than 1000 have at least one digit of 0?

 

10 *9  + 9  = 99   have an ending digit of 0

9*9  = 81  have a middle digit of 0  [ but not an ending digit of 0 ]

 

So

 

99 + 81   =   180 have at least one 0

 

 

cool cool cool

 May 25, 2019
 #2
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1 digit number = 0 cases

2 digit number = 9 x 1 = 9

3 digit number : 9 x 9 x 1 + 9 x 1 x 9 + 9 x 1 x 1 = 171

Finally, add 1000 as last number.

Total numbers containing 0 as one of its digits = 0 + 9 + 171 + 1 = 181.

 May 27, 2019
 #3
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EP: The question says "Less than a 1000". So, Cphill's answer is correct.

 May 27, 2019

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