SOLUTION: A disc jockey must play 14 commercial spots during 1 hour of a radio show. Each commercial is either 30 seconds or 60 seconds long. If the total commercial time during 1 hours 11

Question 145688: A disc jockey must play 14 commercial spots during 1 hour of a radio show. Each commercial is either 30 seconds or 60 seconds long. If the total commercial time during 1 hours 11 minutes, how many 30-second commericals were played that hours? How many 60-second commercials?
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
A disc jockey must play 14 commercial spots during 1 hour of a radio show. Each commercial is either 30 seconds or 60 seconds long. If the total commercial time during 1 hours 11 minutes, how many 30-second commericals were played that hours? How many 60-second commercials?
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Let # of 30 second spots be "t":
Let # of 60 second spots be "s":
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EQUATIONS:
Quantity equation: t + s = 14
Time equations : 30t + 60s = 71 seconds
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t = 14-s
Substitute to get:
30(14-s)+ s = 14
420-29s = 14
29s = 406
s = 14 (# of sixty second spots)
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Substitute into t = 14-s to get:
t = 14-14 = 0 (# of thirty second spots)
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Cheers,
Stan H.

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