Radon-219 has a half-life of about 4 s. After 20 s, how many milligrams of a 500 mg sample will remain?

435.3 mg

211.6 mg

31.3 mg

15.6 mg

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The line plot below represents the number of letters written to overseas pen pals by the students at the waverly middle school. each x represents 10 students. how many students wrote more than 6 and fewer than 20 letters. a.250 b.240 c.230 d.220