Draw your Venn Diagram
My drawing shows that
Note:
Pr(Junior or Psy)= Pr(Jun)+ Pr(Psy)-Pr(Junior AND Psy)
But you are given Pr (NOT(Junior Or Psy), so Pr(Junior or Psy)=1-Pr( Not(junior or Psy).
Finally, then
Pr(Junior ANd Psy)=Pr(Jun)+Pr(Psy)-Pr(Jun or Psy)
= Pr(Jun)+ Pr(Psy)-(1-Pr(NOT(Jun or Psy))
= 13/50 + 20/50-1+24/50
=57/50-1= 7/50
so 7 Psy majors are Juniors.
check my thinking.
This is not physics. Please don't misrepresent your subject again.
A class has 50 students. 13 are juniors, 20 are psych majors, and 24 are neither psych majors nor juniors. How many psych majors are juniors?
1 answer