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We call a number peachy if every digit in the number is either a 3  or next to a 3 For example, the numbers   333, 83, 303 and 3773  are all peachy, but the numbers  32523, 786,  and 3999 are not peachy. How many positive 2-digit numbers are peachy?
 

 Oct 7, 2022
 #1
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We can break into cases:

 

33 - 1 number

3* - 10 numbers

*3 - 9 numbers

 

So the answer is 1 + 10 + 9 = 20.

 Oct 7, 2022
 #2
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I had got that too, however it had marked it wrong. I'm not sure hwt to do now...

Guest Oct 7, 2022
 #3
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it had marked it wrong  

 

 

The second line  3* - 10 numbers  includes a 33  

 

and so does the third line *3 - 9 numbers

 

but you already counted 33 on the first line  

 

so you counted 33 three times

 

Does the book say the actual answer is 18?  

.

Guest Oct 8, 2022
edited by Guest  Oct 8, 2022

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