osanseviero
In a school there are 300 matriculated students (some probability problems)
Delete
Share
This Question is Closed
osanseviero
Best Response
You've already chosen the best response.
0
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
Best Response
You've already chosen the best response.
0
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
Best Response
You've already chosen the best response.
0
|dw:1383272509491:dw|
osanseviero
Best Response
You've already chosen the best response.
0
a. So 210/300=7/10
HawkCrimson
Best Response
You've already chosen the best response.
1
id say so too
osanseviero
Best Response
You've already chosen the best response.
0
How to do the second?
HawkCrimson
Best Response
You've already chosen the best response.
1
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 :(
HawkCrimson
Best Response
You've already chosen the best response.
1
cause apparently in that class there is half of a student :'(
osanseviero
Best Response
You've already chosen the best response.
0
wait a sec, please
osanseviero
Best Response
You've already chosen the best response.
0
lol
HawkCrimson
Best Response
You've already chosen the best response.
1
haha xD
well there 90 students not in the class, and only 15% of the 90 pass, so 90 x 15/100
osanseviero
Best Response
You've already chosen the best response.
0
90 persons is the 30% of total
osanseviero
Best Response
You've already chosen the best response.
0
are you sure?
HawkCrimson
Best Response
You've already chosen the best response.
1
and then 27/2 / 300 = 9/200
HawkCrimson
Best Response
You've already chosen the best response.
1
umm, i thought i was xD
osanseviero
Best Response
You've already chosen the best response.
0
27/2 is the number of persons that got a good grade
HawkCrimson
Best Response
You've already chosen the best response.
1
and didnt come to class but now idk
HawkCrimson
Best Response
You've already chosen the best response.
1
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
Best Response
You've already chosen the best response.
0
Can you repeat your reasoning again? (sorry)
HawkCrimson
Best Response
You've already chosen the best response.
1
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
Best Response
You've already chosen the best response.
0
Ok, I see now :D
osanseviero
Best Response
You've already chosen the best response.
0
And for the third question?
osanseviero
Best Response
You've already chosen the best response.
0
We know that 9 people that did not entered got good grades.
We need to see the ones that did come in
osanseviero
Best Response
You've already chosen the best response.
0
So 80% of 210
HawkCrimson
Best Response
You've already chosen the best response.
1
it would be
210 x 80/100 + 27/2
osanseviero
Best Response
You've already chosen the best response.
0
168 entered and passed, 9 entered and passed, so 176
HawkCrimson
Best Response
You've already chosen the best response.
1
y 9?
osanseviero
Best Response
You've already chosen the best response.
0
the 9 did not enter and did pass*
osanseviero
Best Response
You've already chosen the best response.
0
Sooo...176...and 44/75 (check please)
osanseviero
Best Response
You've already chosen the best response.
0
Probability of entering and getting a good grade
HawkCrimson
Best Response
You've already chosen the best response.
1
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
HawkCrimson
Best Response
You've already chosen the best response.
1
so 195/2 students pass
and the probability of the teacher choosing one is
195/2 /300
osanseviero
Best Response
You've already chosen the best response.
0
Sorry, internet crashed
osanseviero
Best Response
You've already chosen the best response.
0
So 181.5/300
osanseviero
Best Response
You've already chosen the best response.
0
Weird numbers :/
osanseviero
Best Response
You've already chosen the best response.
0
Last one is: Chance of selecting a student that have passed and entered the class
osanseviero
Best Response
You've already chosen the best response.
0
7/10 * 8/10 = 56/100 = 38/50= 19/25
osanseviero
Best Response
You've already chosen the best response.
0
So,...yes?