Statistics Stock Combinations

Statistics
Tutor: None Selected Time limit: 1 Day

The price for the stock of Amazon.com can go either up or down during each trading day.  It’s closing price at the end of the day will be either higher or lower than its price that closed the previous day. Consider a 5 week time period with n=25 trading days. How many combinations are there where the stock goes up on x=20 of the days and down on the other n-x=5 days?

Jul 29th, 2015

Thank you for the opportunity to help you with your question!

combination formulae

ncr

up=25c5

  =53130

Please let me know if you need any clarification. I'm always happy to answer your questions.
Jul 29th, 2015

I you show me the work?

Jul 29th, 2015

here are the workings

ncr=n!/r!(n-r)!

n=25

r=5

replace values in the equation

  =25!/5!.20!

  =[25.24.23.22.21.20/5.4.3.2.1.20]! simplify by canceling 

  =(5.6.11.7.23)

  =53130


Jul 29th, 2015

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Jul 29th, 2015
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Jul 29th, 2015
Dec 3rd, 2016
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