Bunuel wrote:

While taking a certain standardized exam, Dave has 20 minutes to finish his 600-word essay. Over the first 10 minutes, he averages 15 words per minute. By what percent must he increase his average words per minute to finish his essay in the remaining time?

A. 75%

B. 100%

C. 150%

D. 200%

E. 300%

We are given that Dave needs to complete an essay in 20 minutes. Over the first 10 minutes, he averages 15 words per minute and thus competes 10 x 15 = 150 words, which means he has 600 - 150 = 450 words to complete in 10 minutes. That means he needs to average 450/10 = 45 words per minute in the last 10 minutes. We need to determine by what percentage his rate must increase to finish the essay on time. We can let x = the percentage increase and create the following equation to determine x:

15(1 + x/100) = 45

1 + x/100 = 3

x/100 = 2

x = 200

Answer: D

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Head of GMAT Instruction

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