If A worked alone for 2 hours, B worked alone for 4 hours, how many hours will it take C alone to finish?

A finishes the job in 10 hours, B finishes in 12 hours and C finishes the job in 15 hours

If A worked alone for 2 hours, B worked alone for 4 hours, how many hours will it take C alone to finish?
2*(1/10) + 4*(1/12) + C*(1/15) = 1


2/10 + 4/12 + C/15 = 1


C/15 = (1 - 2/10 - 4/12)


C/15 = (60/60 - 12/60 - 20/60)


C/15 = 28/60 = 7/15





C/15 = 7/15


C = 7





It will take C alone another 7 hours to finish the job.
Reply:A would finish 1/5th of the work, B would finish a further 4/12ths of the work, the work remaining would be


=1 - 1/5 - 1/3


=15/15 - 3/15 - 5/15


=15/15-8/15


=7/15 of the work left. At 1/15th of the work each hour it would take C 7 hours.
Reply:A can complete the work in 2 hours


In one hour A will finish (1/2) of the work


B can complete the work in 4 hours


In one hour B will finish (1/4) of the work


If A %26amp; B work together,


in one hour [(1/2)+(1/4)] = (3/4) work can be completed.


Hence, to complete the full work at this rate {1/(3/4)} hours is required.


{1/(3/4)} = 4/3 = 1⅓ hours = 1 hr 20 min


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Reply:7 hours
Reply:A completes 1/5 of the job. B then completes 1/3 of the job...





6/30 + 10/30 = 16/30 (so there is 14/30 of the job left.)





In 1 hour C completes 1/15 of the total job......


14/30 / 1/15 = 7 hours to finish the job.