Online Course Discussion Forum

MC II-B Questions

 
 
Picture of Derek Wong
MC II-B Questions
by Derek Wong - Sunday, 6 January 2019, 8:08 AM
 

Hello Mr. David and everyone! Happy New Year!

I have a question on how to do 4.26, 4.27, and 4.29. Thanks.


(side note: to II-A people, I think we have the same questions so if any of y'all willing to help, I'd be so grateful :D. Thanks again)

 
Picture of David Reynoso
Re: MC II-B Questions
by David Reynoso - Thursday, 10 January 2019, 11:13 AM
 

Hey Derek!

For 26, try using complementary counting: how many regions would you have in a Venn diagram with three sets like the one described in the problem? Use this to find the total number of ways you could choose the sets $A$, $B$ and $C$. Then do the same assuming you only have two sets, this should help counting what happens when $A=\varnothing$.

On 27, try using PIE. Consider a set of numbers where $1$ is adjacent to $2$, and another where $1$ is adjacent to $0$. (Be careful not to accidentally count $6$-digit numbers that start with $0$, it might be a good idea to count when you have $01$ and $10$ separately).

For 4.29 try to proceed similar to example 4.9: Consider five sets that count the number of ways are there so that a specific person leaves with their own coat. Then use this sets and PIE to count how many ways there are so that at least one person leaves with their own coat.