Multiple choice

David is twice as efficient as George and together they can finish a work in 30 days. How many days will George take to complete the work alone?

  1. 90

  2. 85

  3. 80

  4. 75
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A Correct answer
Explanation

Let George's efficiency be x, then David's is 2x. Combined efficiency = 3x. Together they finish in 30 days, so total work = 3x * 30 = 90x. George alone takes 90x / x = 90 days.

AI explanation

Since David is twice as efficient as George, the ratio of their efficiencies is 2 to 1, meaning David takes half the time George takes. Let the time taken by George be x days, so David takes x divided by 2 days. Their combined work rate is 1 divided by x plus 2 divided by x, which equals 1 divided by 30. Solving 3 divided by x equals 1 divided by 30 gives x equal to 90 days.

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