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At a party at the middle school over on Third Avenue next to the bank, 60% of the students are seventh graders. These students are joined by 20 more eighth graders, all of whom like to dance. The party is now 58% seventh graders. How many students are now at the party?

 Mar 25, 2021
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Call the original  number of students, S...and the number of girls  = .60S

Total students  after 20 boys arrive = S + 20

 

Also:

 

Number of  girls divided by total number of students  =  58%

 

.6S  / ( S + 20 )  =   .58    multiply both sides by  S +  20

 

.6S  = .58( S + 20 )

 

.6S  = .58S + 11.6   subtract  .58S from  both sides

 

.02S = 11.6   divide both sides  by .02

 

S  = 11.6 / .02 =    580

 

So...the total number of students = 580 + 20  = 600 smiley

 Mar 27, 2021

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