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CAHSEE Math 5.2 Statistics, Data, and Probability I 193 Views
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Description:
Statistics, Data, and Probability I: Drill Set 5, Problem 2. What is the probability she will pull out a 20, and likely be the creature's first victim?
Transcript
- 00:03
Here's a shmoopy problem for you...
- 00:05
Mrs. Dolthauser insists on every activity being fairly organized...
- 00:10
...even a student evacuation when the school is under attack by a mutant sea creature.
- 00:15
Dolthauser's 20 students are randomly drawing numbers out of a bag to determine
- 00:19
the order in which they are able to get the heck out of there.
Full Transcript
- 00:22
Each student gets to keep the numbered piece of paper that he or she draws out of the bag.
- 00:26
Jose picks first and draws a 10, so he will go tenth, behind nine other students.
- 00:32
Jenna picks next.
- 00:33
What is the probability that she will pull out a 20...
- 00:36
and likely be the creature's first victim?
- 00:38
And here are the potential answers...
- 00:42
OK, so what is this question really asking?
- 00:45
Well, it's a slightly more complicated probability question with a twist.
- 00:49
That is, if it only asked for the odds of pulling one number out of 20 random numbers,
- 00:54
that'd be pretty straightforward right, but Jose has gone and made things more complicated for us.
- 01:00
Why? Because he stuck his number in his pocket.
- 01:02
Because in this case, one number is now being removed -- so the total is no longer 20 -- it's 19.
- 01:10
So Jenna is drawing for a card labeled "20" out of only 19 possible choices.
- 01:16
So her odds are now... one in 19.
- 01:20
With the 10th card removed from the deck,
- 01:22
her odds of drawing the 20th number just went UP.
- 01:26
The answer is B.
- 01:28
Sadly, Jenna does indeed pick the 20.
- 01:31
Fortunately for her though, the sea creature likes its meat... well done.
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