Question

.. A takes 5 days more than B to do a certain job and
9 days more than C; A and B together can do the
job in the same time as C. How many days A would
take to do it?​

Answer 1

A takes 15 days

Let total work = 1.

Time taken by A = t

—> Time taken by B = t - 5

—> Time taken by C = t - 9

Given, 1/t + 1/(t - 5) = 1/(t - 9)

—> (2t - 5)(t - 9) = t(t - 5)

—> t^2 - 18t + 45 = 0

—> (t - 15)(t + 3) = 0

—> t = 15