Q:
      
      
         
            
A can do a work in 9 days, B can do a work in 7 days, C can do a work in 5 days. A works on the first day, B works on the second day and C on the third day respectively that is they work on alternate days. When will they finish the work ?
         
       
      
      
      
          
      
      
          Answer & Explanation
         Answer: C) [6 + (261/315)] days         
         
Explanation: After day 1, A finishes 1/9 of the work.
After day 2, B finishes 1/7 more of the total work. (1/9) + (1/7) is finished.
After day 3, C finishes 1/5 more of total work. Total finished is 143/315.
So, after day 6, total work finished is 286/315.
 
Now remaining work =  29 /315
 
On day 7, A will work again 
 
Work will be completed on day 7 when A is working. He must finish 29/315 of total remaining work.
 
Since he takes 9 days to finish the total task, he will need 261/315 of the day. 
 
Total days required is 6 + (261/315) days.
       
      
      
      
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