A, B and C can do a piece of work in 10 days, 12 days and 15 days respectively. How long will they take to finish it if they work together?
Number of days A required do a piece of work : 10
Number of days B required do a piece of work : 12
Number of days C required do a piece of work : 15
Work done by A in one day: 
Work done by B in one day: 
Work done by C in one day: 
Work done by A, B and C together in one day: 
= 
= 
They can do the work together in 4 days .
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