16. 
X and Y can do a piece of work in 20 days and 12 days respectively. X started the work alone and then after 4 days Y joined him till the completion of the work. How long did the work last? 


17. 
Ravi and Kumar are working on an assignment. Ravi takes 6 hours to type 32 pages on a computer, while Kumar takes 5 hours to type 40 pages. How much time will they take, working together on two different computers to type an assignment of 110 pages? 


18. 
A is 30% more efficient than B. How much time will they, working together, take to complete a job which A alone could have done in 23 days? 


19. 
A, B and C can complete a piece of work in 24, 6 and 12 days respectively. Working together, they will complete the same work in: 


20. 
Sakshi can do a piece of work in 20 days. Tanya is 25% more efficient than Sakshi. The number of days taken by Tanya to do the same piece of work is: 

