Two different age groups were surveyed about the amount of time they spent on social media.
The results are shown in the two frequency
polygons below. The same time intervals were
used for both graphs.
a) How many 15-year old
students took part in
the survey?
Frequency
11-year old students
15-year old students
80
801
70
70
60
60
50
50
640
30
30
20
20
10
10
0
0
0 10 20 30 40 50 60 70 80 0 10 20 30 40 50 60 70 80
Time (mins)
Time (mins)
h
Frequency
540
b) How many more 15-year
old students than 11-year
old students spent
between 35 and 45 mins
on social media?