$A$ is $25\%$ more efficient than $B$. If $B$ alone takes $15$ days, $A$ alone takes:

$A$ is $25\%$ more efficient than $B$. If $B$ alone takes $15$ days, $A$ alone takes:
  1. $10$ days
  2. $11$ days
  3. $12$ days
  4. $\dfrac{75}{4}$ days

Solution

$A$'s rate $= 1.25 \times B$'s rate $= 1.25 \times \dfrac{1}{15} = \dfrac{1.25}{15} = \dfrac{1}{12}$. So $A$ takes $12$ days.

Asked in: IMO

Practice more DIRECT AND INVERSE PROPORTIONS questions on Aicharya