Question

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

Answer 1

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

Answer 2

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

Answer 3

a. So 210/300=7/10

Answer 4

id say so too

Answer 5

How to do the second?

Answer 6

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 :(

Answer 7

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

Answer 8

wait a sec, please

Answer 9

lol

Answer 10

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

Answer 11

90 persons is the 30% of total

Answer 12

are you sure?

Answer 13

and then 27/2 / 300 = 9/200

Answer 14

umm, i thought i was xD

Answer 15

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

Answer 16

and didnt come to class but now idk

Answer 17

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

Answer 18

Can you repeat your reasoning again? (sorry)

Answer 19

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

Answer 20

Ok, I see now :D

Answer 21

And for the third question?

Answer 22

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

Answer 23

So 80% of 210

Answer 24

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

Answer 25

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

Answer 26

y 9?

Answer 27

the 9 did not enter and did pass*

Answer 28

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

Answer 29

Probability of entering and getting a good grade

Answer 30

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

Answer 31

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

Answer 32

Sorry, internet crashed

Answer 33

So 181.5/300

Answer 34

Weird numbers :/

Answer 35

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

Answer 36

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

Answer 37

So,...yes?