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Q.8 The rainfall (in mm) in a city on 7 days of a certain week was recorded as follows:

(i) Find the range of the rainfall in the above data.
(ii) Find the mean rainfall for the week.
(iii) On how many days was the rainfall less than the mean rainfall?
Answer :

(i) Maximum rainfall = 20.5 mm
Minimum rainfall = 0.0 mm
Range = Maximum rainfall – Minimum rainfall
= 20.5 mm – 0.0 mm = 20.5 mm
(ii) Mean rainfall $$\frac{sum of all observations}{number of observation}$$ $$=\frac{0.0+12.2+2.1+0.0+20.0+5.5+1.0}{7}=\frac{41.3}{7}=5.9mm $$ iii) Number of days on which the rainfall was less than the mean rainfall = Monday, Wednesday, Thursday, Saturday, Sunday = 5 days.