(Q17). The following table gives the literacy rate (in percentage) of 35 cities. Find the mean literacy rate.

Literacy rate in %	45-55	55-65	65-75	75-85	85-95
Number of cities	3	10	11	8	3

Solution :

Number of days	Number of students (fi)	Class marks xi	ui = xi - a h	fiui
45-55	3	50	-2	-
55-65	10	60	-1	-
65-75	11	70 a	0
75-85	8	80	1
85-95	3	90	2
-	∑fi = 35	-	-	∑fiui = -

Here a = 70, h = 10,

Now,