There are 50 workers in a small industry. The dialy income of them is Rs. 9 Amongst them, the daily income of the 30 workers, working in the morning is Rs. 8 . Then find the daily average income of workers working in the evening.

Explanation

Here, the total number of workers, n =50
The number of workers in the morning `n_(1)=30`
`therefore ` The numbers of workers in the eveing `n_(2)=n-n_(1)=50-30=20`
The average daily income of the total workers =Rs. 9
The average daily income of the workers in the morning , `barx_(1)=Rs. 8`
According to the law of collective average,
`barx=(n_(1)barx_(1)+n_(2)barx_(2))/(n_(1)+n_(2)) therefore 9=(30xx8+20barx_(2))/(30+20)` or , `9=(240+20barx_(2))/(50)`
or , `450=240 + 20 barx_(2) ` or , `20 barx_(2)=210` or , `barx_(2)=(210)/(20)=10.50`
`therefore ` THe daily income of the workers in the evening =Rs. 10.50.