Sixteen students study Algebra, 21 study Biology, and there are 30 students in all. What is the probability that a student chosen at random studies Algebra or Biology?

Answer 1

A=16

B =21

T=30

at least 7 study both algebra and biology 16+21-30 = 7

possibly 16 study both algebra and biology, with 9 not studying either

the students Not studying either is between 0 and 9. 0<N<9

probability of selecting a student at random who studies either algebra or biology is 1 - N/30= (30-N)/30 where 0<N<9

(30-9)/30 = 21/30= 7/10

Probability is between 100% and 70%