GRE Numeric Entry Explanation

7. The amount of time taken to paint a wall is inversely proportional to the number of painters working on the job. If it takes 3 painters 5 days to complete such a job, how many days longer will it take if there are only 2 painters working?

Correct Answer: 2.5

Explanation:

For inverse proportions remember the formula x₁y₁ = x₂y₂
Here initial painters x days = final painters x days; 3 x 5 = 2 x days
Total days taken will be 15/2 = 7.5, but there is a catch: you were asked how much longer it would take. Initial time was 5 days so it will take 2.5 days longer.

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