SOLUTION: Jamey wanted to understand whether students at her school were in favor of an extended school day. She surveyed some students and displayed the results in the table below: I

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Question 1012311: Jamey wanted to understand whether students at her school were in favor of an extended school day. She surveyed some students and displayed the results in the table below:

In favor Opposed Undecided
Grade 9 5 3 9
Grade 10 8 12 9
Grade 11 15 16 10
Grade 12 12 6 11

If the principal randomly selects a student in grade 9 from this survey, what is the probability that the student is in favor of extending the school day?

Answer by jim_thompson5910(35256)   (Show Source): You can put this solution on YOUR website!
Given Table:
In FavorOpposedUndecided
Grade 9539
Grade 108129
Grade 11151610
Grade 1212611


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Let's add on the totals (row totals and column totals). These values represent the sum along the rows or columns.

In FavorOpposedUndecidedTotal
Grade 953917
Grade 10812929
Grade 1115161041
Grade 121261129
Total403739116


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"If the principal randomly selects a student in grade 9 from this survey"

So we're just focusing on the "grade 9" row. There are 17 students in this grade. There are 5 who are in favor, so

P(In favor | grade 9) = (# who are in grade 9 AND in favor)/(# who are in grade 9)

P(In favor | grade 9) = 5/17
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As a fraction, the probability is 5/17
As a decimal, the probability is approximately 0.2941176 (used a calculator)
As a percentage, the probability is approximately 29.41176%

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