In a class with 20 kids, 1/2 of the students have already fallen asleep so 20/2 = <<20/2=10>>10 kids are already asleep
We start with 20 kids awake and 10 are already asleep so 20- 10 = <<20-10=10>>10 kids are still awake
1/2 of these 10 kids fall asleep next meaning there are 10/2 = <<10/2=5>>5 students still awake
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