Answer:
150 minutes (2.5 hours)
Step-by-step explanation:
We must consider that the total time that the radio program lasted represents the 100%.
Of that 100% we are told that 20% is dedicated to commercials. So the 30 minutes of commercials correspond to 20% of the air time, which can be represented in the following table:
Percentage of time time
20% ⇒ 30min
and we are looking for how long the show was on the air (the 100%).
So updating the table( I will call x the total time on the air):
Percentage of time time
20% ⇒ 30min
100% ⇒ x
This reationship between three values can be solve by the rule of three: multiply the cross quantities on the table (100 by 30) and divide by the remaining amount (20):
x = 100*30 / 20
x= 3000 / 20
x = 150 minutes
The radio show was 150 minutes (2.5 hours) long.
