Question

A can complete a task in 15 days. B is
50% more efficient than A. Both A and B
started working together on the task and
after few days, B left task and A finished
the remaining 1/3 of the given work. For
how many days A and B worked
together?
TRRB Clerk (Pre) 2017]
(a) 3 (6) 5 (c) 4 (d) 6
(e) 2​

Answer 1

A will complete work in 15 days and its efficiency is $\frac{1}{15}$

B's efficiency is  $\frac{1}{15}$ +  $\frac{1}{2}$.$\frac{1}{15}$

=  $\frac{1}{10}$

Hence B can complete work in 10 days.

A and B together can complete work in

=>By adding efficiencies

=>$\frac{1}{10}$ + $\frac{1}{15}$

=>$\frac{5}{30}$

=>taking inverse

=> 6 days

So A and B together worked for $\frac{2}{3}$ x 6

i.e 4 days

Hence correct answer is option C