WAEC 2018 · Paper 2 · Q6

Age (years) 20–24 25–29 30–34 35–39 40–44 45–49 50–54 55–59
Number of workers 22 24 30 38 36 30 18 12

The table shows the age distribution of workers in a factory.

  1. (a)

    Using a graphical method, find the modal age of the workers.

Try it on a graph

Histogram with the crossed lines that locate the mode.

Worked solution (try it first)
  1. Draw the histogram: the modal class is 35–39, with the tallest bar (38).
  2. On the modal bar, join each top corner to the top corner of the opposite neighbour (30 on the left, 36 on the right).
  3. Read down from where the lines cross.
  4. By calculation: 34.5+38−30(38−30)+(38−36)×5=34.5+810×534.5 + \dfrac{38 - 30}{(38 - 30) + (38 - 36)} \times 5 = 34.5 + \dfrac{8}{10} \times 5
    =38.5= 38.5 years.

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