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?
We can break into cases:
33 - 1 number
3* - 10 numbers
*3 - 9 numbers
So the answer is 1 + 10 + 9 = 20.
I had got that too, however it had marked it wrong. I'm not sure hwt to do now...
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?
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