If $A$ is twice as fast as $B$ and together they finish a job in $12$ days, then $A$ alone takes:

Question

Aicharya · Accepted Answer

$A$'s rate $= 2r$, $B$'s rate $= r$. Together $3r = \dfrac{1}{12}$, so $r = \dfrac{1}{36}$ and $A$'s rate $= \dfrac{2}{36} = \dfrac{1}{18}$. $A$ alone $= 18$ days.

If $A$ is twice as fast as $B$ and together they finish a job in $12$ days, then $A$ alone takes:

Solution