Question 201482
A disc jockey must play 16 commercial spots during 1 hour of a radio show. Each commercial is either 30 seconds long or 60 seconds long. If the total commercial time during 1 hour is 13 min, how many 30 second commercials were played that hour? How many 60 second commercials?
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Quantity Equation: s + t = 16
time Equation: 60s + 30t = 13*60
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Simplify
s + t = 16
2s + t = 26
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Subtract 1st from 2nd to get:
s = 10 (# of sixty second commercials)
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Substitute to solve for "t":
10 + t = 16
t = 6 (# of thirty second commercials)
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Cheers,
Stan H.