Question

When Sholey screened on the TV there was a commercial break of 5 min after every 15 min of the movie. If from the start of the movie to the end of the movie there was in all 60 min of commercials that was screened what is the duration of the movie ?\[\]
A.180 min\[\]
B. 195 min\[\]
C.169 min\[\]
D.165 min\[\]

Answer 1

Hint: We find the number of commercials from the duration of one commercial or break of 5 minutes and the total duration of commercials as 60 minutes using a unitary method. We find the duration of the movie by adding the time the movie played before it was interrupted by a commercial break and the final 15 minutes of climax credit roll after which no commercial will be displayed. \[\]

Complete step-by-step solution
We are given in the question that when Sholey screened on the TV there was a commercial break of 5 min after every 15 min of the movie. \[\]
We are also given the question that from the start of the movie to the end of the movie there was in all 60 min of commercials. We are asked to find the duration of the movie. We use the unitary method to find the number of commercials. \[\]
The number of commercials in 5 minutes is 1 then the number of commercials in 1 minute is $\dfrac{1}{5}$. So the total number of commercials in 60 minutes is 60 times $\dfrac{1}{5}$ which is
\[60\times \dfrac{1}{5}=\dfrac{60}{5}=12\]
So the number of times the movie played before it was interrupted by a commercial is 12. We see that there are no commercials to be played after the end of the movie or the beginning of the movie. All the commercials are played during the screening of the movie. So the total amount of time the movie played before 12 commercials in minutes is
\[15\times 12=180\]
We have another 15 minutes which includes climax and the credit roll after which no commercials will be played. So we have total screening time in minutes is
\[180+15=195\]
So the correct option is A.

Note: Most students make the mistake of calculating the total duration of screening as $12\times 20=240$ minutes and then subtracting the duration of commercials $240-60=180$ to choose incorrect option A. We note that the unitary method is a technique for solving a problem by first finding the value of a single unit, and then finding the necessary value by multiplying the single unit.