Because most of them keep on going for infinite. For example,

is an irrational number that goes on forever 3.14159 etc etc etc
Due to that situation, I came to conclusion that is is case control study. It's a kind in wich students who have specific conditions are compared with students who don't have it.
Answer:
auxiliary lines.
Step-by-step explanation:
Determine the ratio of defective telephones
ratio = 9/30
ratio = 3/10
3 of 10 telephones are defective
Determine the number of defective telephones each day
def telephone = ratio of defective × total production
def telephone = 3/10 × 1000
def telephone = 300
There are 300 defective telephones each day