MHB What is the Probability of Getting 13 out of 46?

  • Thread starter Thread starter karush
  • Start date Start date
  • Tags Tags
    Probability
AI Thread Summary
The discussion centers on calculating the probability of selecting 13 boys from a total of 46 students. One participant initially miscalculates the total possibilities by not considering that the selection is limited to boys. The correct probability should reflect the ratio of boys who watch television to the total number of boys. The final consensus indicates that the probability is expressed as 13 out of 46. Accurate understanding of conditional probabilities is emphasized throughout the conversation.
karush
Gold Member
MHB
Messages
3,240
Reaction score
5
View attachment 1210

the numbers in () and boxes are mine, easy problem but still can make mistakes..(Wasntme)
 
Mathematics news on Phys.org
karush said:
View attachment 1210

the numbers in () and boxes are mine, easy problem but still can make mistakes..(Wasntme)

Hey karush!

Your table looks just fine and so is your answer to the first question.

However, for the second question, you have to consider what the total number of possibilities is. Apparently you thought it was a 100, but then you did not take into account that it is given that it is a boy. You should look only at the boys.
 
I like Serena said:
Hey karush!

Your table looks just fine and so is your answer to the first question.

However, for the second question, you have to consider what the total number of possibilities is. Apparently you thought it was a 100, but then you did not take into account that it is given that it is a boy. You should look only at the boys.

see what you mean, so it should be $\displaystyle\frac{13}{38}$
 
karush said:
see what you mean, so it should be $\displaystyle\frac{13}{38}$

Nope. Not yet.
It should be the number of boys that watch television divided by the total number of boys.
You just calculated the probability that a student is a boy, given that (s)he prefers to watch television.
 
$\displaystyle\frac{13}{46}$ :cool:
 
Seemingly by some mathematical coincidence, a hexagon of sides 2,2,7,7, 11, and 11 can be inscribed in a circle of radius 7. The other day I saw a math problem on line, which they said came from a Polish Olympiad, where you compute the length x of the 3rd side which is the same as the radius, so that the sides of length 2,x, and 11 are inscribed on the arc of a semi-circle. The law of cosines applied twice gives the answer for x of exactly 7, but the arithmetic is so complex that the...
Back
Top