Question

A milk centre sold milk to 50 customers. The table below gives the number of customers and the milk they purchased. Find the mean of the milk sold by direct method.

Milk Sold (Litre)	1 - 2	2 - 3	3 - 4	4 - 5	5 - 6
No. of Customers	17	13	10	7	3

Answer 1

Class (Milk sold in litres)	Class Mark xi	Frequency (Number of customers) fi	Class mark × Frequency xifi
1 - 2	1.5	17	25.5
2 - 3	2.5	13	32.5
3 - 4	3.5	10	35
4 - 5	4.5	7	31.5
5 - 6	5.5	3	16.5
		$\sum _{}{f}_i=50$	$\sum _{}{x}_i{f}_i=141$

Mean = $\frac{\sum _{}{x}_i{f}_i}{\sum _{}{f}_i}$
​$=\frac{141}{50}$
= 2.82 litres
Hence, the mean of the milk sold is 2.82 litres.