In a survey, 75% of respondents said that they watch TV for one hour each day. If 30 respondents said they watch TV for one hour each day, how many respondents took the survey in total?
Let X be the total number of respondents
The fraction of respondents who said that they watch TV for one hour each day is 75/100 = 3/4
The number of respondents who watch TV for one hour each day is 3/4*X = 3*X/4
If 3*X/4 = 30, 3*X = 120
The number of respondents who took the survey is X = 120/3 = <<120/3=40>>40. Answer: \boxed{40}.