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Help on math challenge1B(c) amc8/mathcounts winter 2017-2018 counting and probability

 
 
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Help on math challenge1B(c) amc8/mathcounts winter 2017-2018 counting and probability
by Weston Zong - Sunday, 14 January 2018, 10:38 AM
 

for 5.18, it says That is, we only care how many of them are both on the same day of the week. What does it mean by that?

 
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Re: Help on math challenge1B(c) amc8/mathcounts winter 2017-2018 counting and probability
by David Reynoso - Tuesday, 16 January 2018, 10:09 AM
 

Say Alice and Charles were born on Tuesday, Bob on Wednesday and Desiree on Friday. We would get the same outcome if say Alice was born on Friday, Bob and Desiree on Tuesday, and Charles on Wednesday. That is 2 people were born on Tuesday, 1 on Wednesday and 1 on Friday.