Multiple choice

$A$ can complete a certain job in $12$ days. $B$ is $60$ % more efficient than $A. B$ can complete the work alone in:

  1. $6$ days
  2. $6.25$ days
  3. $7.2$ days
  4. $7.5$ days
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A's rate = 1/12. B is 60% more efficient, so B's rate = 1.6 * (1/12) = 1.6/12 = 16/120 = 2/15. Time taken by B = 1 / (2/15) = 15/2 = 7.5 days.

AI explanation

Using the efficiency formula, time taken is inversely proportional to efficiency, so B's time equals A's time divided by 1.60. Substituting A's time of 12 days gives 12 / 1.60, which equals 7.5 days.

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