In a school there are 300 matriculated students (some probability problems)

- osanseviero

In a school there are 300 matriculated students (some probability problems)

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- osanseviero

210 of those 300 enter the class. 80% of the students that enter the class get good grades, 15% of the students that dont enter the class get good grades

- osanseviero

If we chose a random matriculated student, which is the probability of him:
1. Being in the class
2. Don't being in the class and getting good grades
3. Getting good grades

- osanseviero

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## More answers

- osanseviero

a. So 210/300=7/10

- anonymous

id say so too

- osanseviero

How to do the second?

- anonymous

first you find how many students that arnt in the class and are getting gud grades so
90 x 15/100 = 27/2
feel sorry for the student that lost a limb :(

- anonymous

cause apparently in that class there is half of a student :'(

- osanseviero

wait a sec, please

- osanseviero

lol

- anonymous

haha xD
well there 90 students not in the class, and only 15% of the 90 pass, so 90 x 15/100

- osanseviero

90 persons is the 30% of total

- osanseviero

are you sure?

- anonymous

and then 27/2 / 300 = 9/200

- anonymous

umm, i thought i was xD

- osanseviero

27/2 is the number of persons that got a good grade

- anonymous

and didnt come to class but now idk

- anonymous

normally when i got half a person it was a sign that something went wrong but my reasoning makes sense atleast to me lol

- osanseviero

Can you repeat your reasoning again? (sorry)

- anonymous

90 students are people that do not come to class, 15% of these students are students that do well in exams. therefore 90 x 15/100 = 27/2

- osanseviero

Ok, I see now :D

- osanseviero

And for the third question?

- osanseviero

We know that 9 people that did not entered got good grades.
We need to see the ones that did come in

- osanseviero

So 80% of 210

- anonymous

it would be
210 x 80/100 + 27/2

- osanseviero

168 entered and passed, 9 entered and passed, so 176

- anonymous

y 9?

- osanseviero

the 9 did not enter and did pass*

- osanseviero

Sooo...176...and 44/75 (check please)

- osanseviero

Probability of entering and getting a good grade

- anonymous

but it should be 168 + 27/2
because the number of students that didnt come to class and are getting gud grades are 27/2

- anonymous

so 195/2 students pass
and the probability of the teacher choosing one is
195/2 /300

- osanseviero

Sorry, internet crashed

- osanseviero

So 181.5/300

- osanseviero

Weird numbers :/

- osanseviero

Last one is: Chance of selecting a student that have passed and entered the class

- osanseviero

7/10 * 8/10 = 56/100 = 38/50= 19/25

- osanseviero

So,...yes?

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