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


Day



Mon



Tue



Wed



Thurs



Fri



Sat



Sun



Rainfall


(in mm)



0.0



12.2



2.1



0.0



20.5



5.5



1.0



(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?


(i) Now,


We have to find the range of the given data.


And,


We know that,


Highest rainfall = 20.5mm


Lowest rainfall = 0.0mm


Thus,


Range = Highest value – Lowest value


Hence,


Range of the given data can be calculated as follows:


Range = highest rainfall – lowest rainfall


= 20.5 – 0.0


= 20.5 mm


(ii) Here,


We have to find the mean of the rainfall for the week


Now,


At first,


We’ll find the sum of all the observations


Thus,


Sum of all the observations = 0.0 + 12.2 + 2.1 + 0.0 + 20.5 + 5.5 + 1.0


= 41.3


Now,


Total number of observations = 7


Hence,


Mean rainfall =


=


= 5.9 mm


(iii) Here,


As per the question,


We have to find that,


The number of days when the rainfall was less than the mean rainfall


Hence,


We can observe that,


For total five days the rainfall was less than the mean rainfall


Now,


These days are as follows:


Monday, Wednesday, Thursday, Saturday and Sunday


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