Question

in a class, 3/5 students have brown hair. if 9 students have brown hair, how many students are in the class in total?

Answer 1

9/3 = 3
3 is 1/5 of the total answer
You do 3*5 and that will equal 15

Answer 2

 The answer is:  15 .

There are 15 (fifteen) total students in the class.
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(3/5) / 9 =  (2/5) / x ;
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Solve for "x" ;  and then add "x + 9" to get the answer;
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 (3/5) x  = (2/5)*9 ;
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 (3/5) x = (18/5) ;
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Multiply BOTH SIDES by "5" ; to get rid of the fraction:
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 5* { (3/5) x = (18/5) } ;
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  to get: 
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        3x = 18 ;
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   Divide each side by "3"; to isolate "x" on one side of the equation; and to solve for "x"
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        3x / 3 = 18 / 3 ;
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    x = 6 ;
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  Now add "9" to this number:
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  x + 9 = 6 + 9 = 15.
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   The answer is:  15 .  

There are 15 (fifteen) total students in the class.
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