Question 984793
work done by all 45 workers in 1 day  = 1/10 of work
work done 1 worker in 1 day  = (1/10)(1/45) of work
                       =1/450 of work

after 4 days , 15 workers laid off
it means that 45 workers works for 4 days
  work done by 45 workers for 4 days  = 4*45 /450 
                           = 4/10  of work
after 4 days , no of workers available  = 45-15 =30
   work remaining  =1 -4/10
         =6/10 of work
30 workers will finish the remaining work in  = 30/(6/10)
                      = 50 days
solution : 50