Question

If man A complete a piece of work in 12 days and
the same work is completed by B and C in 15 days
and 20 days respectively. In how many days the
work is completed if they work together?
(A) 4 days (B) 8 days
(C) 5 days (D) 6 days​

Answer 1

They work together :

• A complete a piece of work in 12 days
• B complete a piece of work in 15 days
• C complete a piece of work in 20 days

   First we take LCM of these numbers 12 , 15 , 20

so,                           LCM is 60                              ( total work is 60 )

A complete whole work in 12 days and total work is 60

then A complete work in  1 day = 60/12 = 5     (efficiency of A )

B complete whole work in 15 days and total work is 60

then B complete work in  1 day = 60/15 = 4     (efficiency of B )

C complete whole work in 20 days and total work is 60

then C complete work in  1 day = 60/20 = 3     (efficiency of C )

now in 1 day A , B and C together complete work = 5 + 4 + 3   = 12

so ,                       total work  = 60

                      A + B + C  =  60/12    = 5 day

so, option C is correct .

Know more

Q.1.-  If a can complete a piece of work in 15 days and B can complete the same work in 12 days how many days will both of them take to complete the work

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Q.3.-  A and b can do a piece of work in 6days b and c in 8days a and c in 12days if they work together and a leaves after 4days how many days remaining b and c complete

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