Question 503671
m = percentage of music majors
s = total students in south campus
n = total students on north campus
s+n = 1000
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so
n = 1000-s
s = 1000-n
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.10n = number of music majors on north campus
.90s = number of students in south campus
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420 of 1000 total students are music majors
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.1n + .9s = 420
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substitute for s = 1000-n
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.1n + .9(1000-n) = 420
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multiply by 10 to remove decimals
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n + 9(1000-n) = 4200
n + 9000 -9n = 4200
-8n = -4800
n = 600
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s = 1000-s
s = 400
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Always check your work.
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.10n = .1(600) = 60
.90s = .9(400) = 360
60+360 = 420
Correct.
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Re-read the question to make sure you answer it.
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Answer:  the north campus had 600 students, and the south campus had 400 students.
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Done.