A company can complete a certain job in 12 days, another company can complete the same job in 9 days, and the third company in 18 days. In how many days can three companies, if they work together, complete the job?

4 days.

Explanation:

Given:

A company can complete a certain job in 12 days.

Another company can complete the same job in 9 days,

And the third company in 18 days.

Question asked:

In how many days can three companies, if they work together, complete the job ?

Solution:

In 12 days, a company can complete = 1 job

In 1 day,  a company can complete = of the job ( one - twelfth part of the job)

Similarly, another  company can complete in 1 day = of the job

And the third company can complete in 1 day = of the job

Now, to find number of days they will take to complete the whole job together,

In 1 day, all the three company can complete = of the job        

By taking LCM of 12, 9 and 18 we get 36         = of the job  

Now, of the job is done in = 1 day

Then the 1 whole job is done in =   ( by unitary method )                                                      

                                                     =

                                                     =

Therefore, three companies can  complete the job in 4 days, if they work together.

um sure

answer; planning;