in a group of 30 studentsall study at least one of the subjects Physics & Biology 20 attendthe phy...cont down

Question

cont-21 attend the bio class find the probability that a student chosen at random studies both physics and biology.

Answer 1

those who study both=11
probability=11/30

Answer 2

30 students

Probability study physics = p(p) = 20/30
Probability study biology = p(b) = 21/30
Probability study neither = p(0) = 0
Probability study both p(p∩b)

p(pUb) = p(p) + p(b) - p(p∩b) = 1 - p(0)
p(p∩b) = p(p) + p(b) - 1 + p(0)
p(p∩b) = 20/30 + 21/30 - 1 + 0 = 11/30