The heights of 60 plants were measured and grouped as follows:
Height (cm): 20–25 | 25–30 | 30–35 | 35–40 | 40–45 | 45–50
Number of plants: 4 | 6 | 12 | 18 | 14 | 6
(a) Draw both the less-than and the more-than cumulative frequency curves on the same graph.
(b) From the point of intersection of the two curves, estimate the median height of the plants.