We may calculate class marks (x_{i}) for each interval by using the relation
x_{i} \(=\frac{Upper\,class\,limit+lower\,class\,limits}{2}\)
Class size = 50
Now taking 225 as assumed mean we can calculate as follows:
Daily expenditure (in Rs) 
f_{i} 
d_{i }= x_{i}  A = x_{i}  225 
u_{i }= \(\frac{xi225}{h}\) 
xi 
f_{i}u_{i} 
100  150 
4 
100 
2 
125 
8 
150  200 
5 
50 
1 
175 
5 
200  250 
12 
0 
0 
225 
0 
250  300 
2 
50 
1 
275 
2 
300  350 
2 
100 
2 
325 
4 

N = 25 



\(\sum\)f_{i}u_{i} = 7 
Mean (x̅) = A + \(\frac{\sum f_iu_i}{N}\times h\)
\(=225+\frac{7}{25}\times50\)
\(=22514=211\)
So mean expenditure on food is 211