10 men working 6 hours a day can complete a week in 18 days .how many hours a day must 15 men work to complete the same work in 12 days ?  

10 men working 6 hours a day can complete a work in 18 days.  so no. of man work hours needed to complete the work is = 10x6x18 

so,when 15 men work, and should complete the work in 12 days,

let,

the no. of hours they work per day be h 

so for the work to be completed the man work hours will be the same  so,

15xhx12=10x6x18  so h=6  so they have to work for 6 hours a day to complete the work in 12 days  Ans:6