The distribution shows the number of days a group of 260 students were absent from school in a term. How many students were absent for at least four days?
No. of days
1
2
3
4
5
6
No. of students
20
x
50
40
2x
60
Worked solution (try it first)
The frequencies add up to 260: 20+x+50+40+2x+60=260, so 170+3x=260.
So 3x=90 and x=30.
The 5-day group is 2x=60 students.
At least four days means 4, 5 or 6 days: 40+60+60=160 students, option C.