Question

The efficiency of A is thrice of B and

half of C. If B alone completes a
work in 45 days, in how many days
can A along with C complete the
same work?
Select one:
5 days
15 days
7.5 days
30 days​

Answer 1

5 days

Explanation:

Number of days taken by B for completion of the work = 45 days.

Efficiency of A is thrice that of B hence he will complete the same task in
`(1)/(3)` rd time of B

Hence number of days A takes to finish the same job =
`(45)/(3)` = 15 days.

Also

Efficiency of A is half that of C , Hence C takes half the time A takes to finish the job. Hence number of days taken by C to Finish the same job =
`(15)/(2)` days

Now,

Amount of work completed by A in a single day =
`(1)/(15)`

Amount of work completed by C in a single day =
`(2)/(15)`

If A and C works together the amount of work completed =
`(1)/(15)  + (2)/(15)`

=
`(3)/(15)`

=
`(1)/(5)`

Hence the number of days taken to finish the job together by A and C = 5 days