Out of the 20 students, 20 x 1/4 = <<20*1/4=5>>5 students stayed in the classroom.
While 20 - 5 = <<20-5=15>>15 students went to the playground.
Out of these 15 students, 15 x 1/3 = <<15*1/3=5>>5 are boys.
Therefore, 15 - 5 = <<15-5=10>>10 girl students from this class are in the playground.
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