Multiple choice

$A$ is $3$ times more efficient than $B$. Hence, he takes $60$ days less in painting a room. In how many days' work will the painting will be completed, if $A$ and $B$ both work together?

  1. $\displaystyle 30$ days
  2. $\displaystyle 45$ days
  3. $\displaystyle 22\frac{1}{2}$ days
  4. $\displaystyle 17\frac{1}{2}$ days
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let B take x days, A takes x/3 days. x - x/3 = 60, so 2x/3 = 60, x = 90. A takes 30 days, B takes 90 days. Together: (30*90)/(30+90) = 2700/120 = 22.5 days.

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