Since the ratio of boys to girls is 3:5, then the class is divided into 3 + 5 = <<3+5=8>>8 parts.
The girls have 5 - 3 = <<5-3=2>>2 parts more than the boys.
Since 2 parts are equal to 4, then 1 part is equal to 4/2 = 2 students.
Hence, there are 8 parts x 2 = <<8*2=16>>16 students.
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