Question 107

A, B and C can do piece ofwork in 30 days, 45 days and 90 days, respectively. A starts the work and heis assisted by B and C togetheron every third day. In how many dayswill the work be completed?

Solution

 A work  = 30 days 

B = 45 days 

C =90 days

then total work 90  (taken LCM  A, B and C work )

Efficiency of A = 3 , B = 2 and C = 1 

then  Day 1 only A work = 3 

Day 2  only A work = 3 

Day 3 A, B, C work together = 6 

12 work every  3 days 

then it repeat 

12 work = 3 days

84 work = 21 days 

remaining work 90-84 = 6 work  

Another 2 days complete work by A 

so total day 21 + 2 = 23 days Ans

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