Question

Raghu can do a job in 12 days alone and sam can do the same job in 15 days alone. A third person aru whose efficiency is two-third of efficiency of both ram and shyam together, can do the same job in how many days alone

Answer 1

Raghu and Sam can do the work in

$\frac{1}{ \frac{1}{12} + \frac{1}{15} } \\ = \frac{20}{3}$

so aru can do it in (20/3)*(3/2)=10 days.

Answer 2

Solution :-

Given : Ram can do a job in 12 days alone and Shyam can do the same job in 15 days alone.

Ram's one day work = 1/12

Shyam' one day work = 1/15

(Ram + Shyam)'s one day work = 1/12 + 1/15

= (5 + 4)/60 = 9/60

Given : A third person Aru whose efficiency is two-third of efficiency of both Ram and Shyam together.

Aru's one day work = 9/60 × 2/3

= 1/10

Hence,

Aru can finish the work alone in 10 days.