Multiple choice

A is 40% more efficient than B. How much time will they both take to complete the same piece of work which A alone can complete in 20 days ?

  1. 7 days

  2. 10(⅓) days

  3. 11(⅔) days

  4. 10 days

  5. None
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Since A is 40% more efficient than B, their efficiency ratio is 140:100, or 7:5. If A completes the work in 20 days, the total work can be represented as 7 * 20 = 140 units. Working together, their combined efficiency is 7 + 5 = 12 units per day, so they will complete the work in 140 / 12 = 11 2/3 days.

AI explanation

Since A is 40 percent more efficient than B, the ratio of their efficiencies is 140 to 100, or 7 to 5. If A takes 20 days to complete the work alone, B will take 20 multiplied by 7/5, which equals 28 days to complete it alone. Let the total work be the LCM of 20 and 28, which is 140 units, making A's daily capacity 7 units and B's daily capacity 5 units. Working together, they complete 12 units per day, so dividing 140 units by 12 gives a completion time of 11(2/3) days.

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