Marie works for an optician. She records the depth of a lens in each of the 100 pairs of glasses on display.
Depth
Her results are summarised in the table.
Number of pairs of glasses
Depth of lens, x mm,
to the nearest mm
10 << 20
5
20 < X < 30
20
30 < x < 40
23
40 <r< 50
52
In which group does the median lie?
(1 mark)
10 < x < 20
20 < x < 30
30 < x < 40
40 < x < 50​