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NT III Chapter 2

 
 
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NT III Chapter 2
by Tina Jin - Saturday, 13 May 2023, 4:27 PM
 

Hello!


I am stuck on 2.22, 2.25, 2.26, 2.30, and 2.32.


Did I do any calculation error for problem 2.25? Each column represents each type of coin and one "tally mark" represents one number of that coin.


Thanks!


Tina Jin

 
Picture of Dr. Kevin Wang
Re: NT III Chapter 2
by Dr. Kevin Wang - Saturday, 27 May 2023, 12:31 AM
 
2.25: pay attention to pennies and dimes.  When you get to "2" and "4", it is incorrect.  Think about their parities (even or odd).

2.26: The operations won't change the total sum mod 3.

2.22: Each digit appear in each place the same number of times, except when 0 is the leading digit.

2.30: Similar to 2.26, consider mod 3.

2.32: for any two integers, their sum and difference have the same parity.