Page 290 - Start Up Mathematics_7

the same argument stands for median also. Moreover, mode and median are
not affected by extreme values, hence they are not useful in finding the total
number of chapattis required. The value of arithmetic mean is 2.72 which helps
us to find the total chapattis, i.e., 2.72 × 25 = 68. Thus, mean is the appropriate
representative value.

EXERCISE 16.1

1. The marks scored by 11 students in Mathematics test are as follows:
34, 37, 30, 38, 50, 34, 34, 38, 36, 45, 31

Find the value of: (a) range (b) arithmetic mean (c) median (d) mode
2. The rainfall in (mm) in a city on 7 days of a certain week is recorded as follows:

Day Monday Tuesday Wednesday Thursday Friday Saturday Sunday
Rainfall 3.5 8.2 0.0 20.5 7.3 1.0 5.0
(a) Find the range of the amount of rainfall from the above data.
(b) Find the mean rainfall for the week.

(c) For how many days was the rainfall more than the average?
3. The weight (in kg) of 15 students of a class are:
39, 42, 33, 45, 36, 47, 35, 44, 49, 40, 37, 39, 44, 39, 44
(a) Find the median weight.

(b) Find the value of mode. Is there more than one mode?
4. Samuel who works in a customer care call centre keeps a record of the number of minutes
each telephone call lasts. The record of the calls is:
10, 25, 31, 31, 19, 13, 26, 26, 19, 10, 13, 20, 26, 19, 26, 19, 26, 30, 28, 26
(a) Convert the data into frequency table.
(b) How many minutes does the longest and shortest call last? Also calculate the range.
(c) Calculate the mean, median and mode.

(d) The customer care call centre wants to know the central tendency which best describes
the situation and is useful in estimating the total time the employees are at work. Can
you help?

Bar Graphs

In the previous class, we have seen how information collected could be first arranged in a frequency
distribution table and then this information could be converted into pictographs or bar graphs.
A bar graph is a pictorial presentation of data which is represented by rectangles of uniform width
with equal spacing between them called bars.

Construction of bar graphs

In a bar graph, each bar or rectangle represents only one value of the numerical data and there
are as many bars as the number of values in the data. Bars are usually drawn vertically on the
horizontal line which is X-axis. The height of the bars depends on the values of the numerical

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