Two motor mechanics, Raju and Siraj, working together can overhaul a scooter in 6 hours. Raju alone can do the job in 15 hours. In how many hours can Siraj alone do it?
Number of hours Raju required to overhaul a scooter : 15 hours
Let number of hours siraj required to overhaul a scooter : X hours
Number of hours required by Raju and Siraj together to do a piece of work : 6 hours
Work done by Raju in one hour: 
Work done by Siraj in one hour: 
Work done by Raju and Siraj together in a one hour : 
Work done by Raju and Siraj together in one hour : 
= 
= 
⇒ 6X +90 = 15X
⇒ 9X = 90
⇒ X = 
= 10 hours
Siraj can do the work 10 hours.
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