The boys outnumber the girls 5 to 2.
That means on the average, out of every 5+2=7 students, 
5 of them are boys and 2 of them are girls.  That means 

5/7ths of the 105 students are boys. 

and 

2/7ths of the 105 students are girls.



You can either get the number of girls by:

1.  Subtracting 105-75 = 30 girls

or

2. 

Edwin
  

Answer by macston(5194)   (Show Source): You can put this solution on YOUR website!
 (5/7)(100%)=per cent boys=71.4%

(2/7)(100%)=percent girls=28.6%

Number of boys=105(.714)=75 boys

Number of girls=105(.286)=30 girls 

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