The water bills (in rupees) of 32 houses in a locality are given below:

30, 48, 52, 78, 103, 85, 37, 94, 72, 73, 66, 52, 92, 65, 78, 81, 64, 60, 75, 78, 108, 63, 71, 54, 59, 75, 100, 103, 35, 89, 95, 73.

Taking class intervals 30 - 40, 40 - 50, 50 - 60, ……, form frequency distribution table.

Construct a combined histogram and frequency polygon.

First represent the given data in the form of a frequency distribution table.

Here, class intervals represent water bills class and frequency represents no. of houses.

Steps of construction of histogram :

1. Take 1 cm along x-axis = 10 units.

2. Take 1 cm along y-axis = 1 unit.

3. Construct rectangles corresponding to the above continuous frequency distribution table.

The required histogram is shown in the adjoining figure.

Steps of construction of frequency polygon :

1. Mark the mid-points of upper bases of rectangles of the histogram.

2. Join the consecutive mid-points by line segments.

3. Join the first end point with the mid-point of class 20 - 30 with zero frequency, and join the other end point with the mid-point of class 110 - 120 with zero frequency.

The required frequency polygon is shown by thick line segments in the diagram.