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A disc jockey must play 14 commercial spots during 1 hour of radio show. Each commercial is either 30 seconds ?

or 60 seconds long. If the total commercial time during 1 hour is 11 minutes, how many 30-second commercials were played that hour? How many 60-second commercials?

Public Comments

1. Ok so first convert 11 mins to seconds - 660 seconds. now set up an equation setting the number of 60 sec commercials as x and 30 second commercials as y : 60x + 30y = 660 then there is 14 spots so x + y = 14. Now you can solve it by multiplying (-60)(x + y = 14) which is -60x + -60y = -840. combine that equation with the first one (60 x + 30y =660) and you get -30y = -180 meaning y equals 6. since there are six 30 sec commercials then there must be eight 60 second commercials. hope i helped! (: