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In this question, we're given the number of hours needed by 6th grade students to complete a research project is given below.
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So over here is the number of hours from 4 to 10 plus and number of students here.
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For instance, 2 students needed 4 hours, 20 students needed 5 hours, so on so forth.
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Now, total number of students will be adding up this column and there'll be 104.
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A student is randomly selected.
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Event a is the event the student took between 6 and 9 hours inclusive.
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Event b is the student took at most 7 hours.
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Event c is the event the student took at least 7 hours.
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We're going to find probability in part a, a or b.
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Now, n is times set notation's intersect or is plus set notation's union.
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Now, a or b, meaning we're looking at probability of a union b.
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Now, event a is the student took between 6 and 9 hours inclusive.
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Union with means we combine.
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Event b is at most 7 hours.
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So we're going to take everything in.
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Now, at most 7 hours means from 4 to 7.
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That's event b.
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Union means we combine with event a that is 6 to 9 hours.
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So we're looking at this portion here.
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So we're taking from 4 to 9 hours inclusive.
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So that would be probability the student took between 4 to 9 hours inclusive.
01:49
So that would be adding all these numbers from 4 to 9, the number of students.
01:58
That would be the number of students who took 4 hours is 22 plus number of students who took 5 hours will be 20.
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So on so forth, add up all the way to 7 students who needed to take 9 hours.
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Now, probability always divide by the total number of possible outcomes.
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In this case, it's the 104 students.
02:24
And so the answer is 49 out of 52 or 0 .942, 3 decimal place.
02:38
B, we want to find probability not c...