6 persons working 8 hours a day earn Rs 8400 in a week
6 persons working 1 hour a day earn Rs \(\frac{8400}{8}\) in a week.
\(\therefore\) 1 person working 1 hour a day earns Rs \(\frac{8400}{6\times8}\) in a week. (less persons, less days, less earnings)
1 person working 6 hours a day earns Rs \(\frac{8400\times9\times6}{6\times8}\) in a week. (more persons, more hours, more earning)
= Rs 9450.
