With the problem, it's best to put this into a fraction
8/20 of every student will be absent from school less than five days a year, which can then be simplified to 2/5.
There are multiple ways to go about this problem, but my preferred way is to then take 1/5th of 400, which can be done by taking 1*400/5 which equals 80. Since we are asking for 2/5's, just multiply that number by 2, which gives us 160 students.
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