20 points for geometry suppose the tree diagram below represents all the students in a high school and that one of these students were chosen at random. if the student is known to be a boy, what is the probability that the student is left-handed? a.3/4 b.1/4 c.1/6 d.5/6

The answer is 1/4 

Explanation

The question focuses on "if the student is known to be a boy..."  we would obviously know that we would focous on only the total of the boys.    

We have the formula for the probability of an event of happening which we would call event A (a boy being left-handed).  P(A)= number of favorable outcomes/ total number of possible outcomes.  The left-handers would go in the favorable outcomes since we want the probability of a boy being left handed and we would place the total boys in the total number of possible outcomes since all of them are going to be the one to be randomly picked.    50 left-handed/ 200 total boys.   We have our fraction that is 50/200 as the probability but we can simplify it!   We simplify 50/200 to get 1/4!!!  1/4 is the probability of a boy being picked that is left-handed!

Hope this helps!