Question

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 1

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.

Answer 2

$\underline{\underline{\Huge\mathfrak{Answer ;}}}$

=> 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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