The monthly salary of some families in a society is given below :

(i) What is the lower limit of the second class interval?
(ii) What is the upper limit of the last class interval?
(iii) What is the class size of each class interval?
(iv) What is the mid-value of the third class interval?
(v) How many families earn Rs. 50,000 or more in a month?
(vi) How many families earn less than Rs. 20,000 in a month?

Explanation

(i) Lower limit of the second class interval = 20.
(ii) Upper limit of the last class interval = 70.
(iii) Class Size=Upper limit - Lower limit= 10.
(iv) Mid-value =`("Upper Limit + Lower Limit")/(2)`
`=(30+40)/2=70/2=35.`
(v) Families earning Rs. 50,000 or more in a month =11 + 5 16.
(vi) Families earning less than Rs. 20,000 in a month =6.