1. If 12 boys can earn Rs. 240 in 5 days, how many boys can earn Rs. 420 in 21 days ?

2. If a certain number of workmen can do a piece of work in 25 days, in what time will another set of an equal number of men do a piece of work twice as great, supposing that 2 of the first set can do as much work in an hour as 3 of the second set can do in an hour ?

3. If 3 men or 6 boys can do a piece of work in 10 days will it take to complete a work twice as large with 6 men and 2 boys working together for 8 hours a day ?