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In a high school with 500 students, 40% of the seniors play a musical instrument, while 30% of the non-seniors do not play a musical instrument. In all, 46.8% of the students do not play a musical instrument. How many non-seniors play a musical instrument?

 May 5, 2020
 #1
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Let's say the number of seniors is x.

 

3/5 x +(3/10 *(500-x)) = 468/1000 * 500

 

3/5 x+150 - 3/10 x = 234

 

3/10 x = 84

 

x = 84 * 10/3 = 280

 

500- x = 220 non seniors

 

220 * 7/10 = 154

 

If you don't understand anythign feel free to ask

 May 5, 2020
 #2
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I have a question, why do you use the 220 instead of 280 whihc you got in your calculations?

 May 5, 2020
 #3
avatar+1502 
+3

x  = 280, and that's the number of seniors. However we are solving for number of non-seniors so 500-280 =220.

hugomimihu  May 5, 2020
 #4
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oh ok

 

also why do you multiply by 7/10?

Guest May 5, 2020
 #5
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+3

we multiply since 100-30  = 70% play musical instruments, and 220 is the TOTAL number of non-seniors.

hugomimihu  May 5, 2020

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