Seventy percent of children who go to the doctor have fevers. Of those with fevers, 30% also have a rash. Of those without fevers, 20% have a rash. What is the probability that a child at the doctor's office with a rash does not have a fever
+128475 For convenience....let there be 100 children who go to the doctor.....so...
100 * .70 = 70 have fevers
70 * .30 = 21 have fevers and rash
100 - 70 = 30 have no fever
30 * .20 = 6 have no fever but have a rash
21 + 6 = 27 have rashes
So
6 have a rash but no fever
_______________________ = 6 / 27 = 2 / 9
27 have a rash
EDIT.....thanks, Geno forspotting my earlier error !!!
