asimov wrote:

If Dave works alone he will take 20 more hours to complete a task than if he worked with Diana to complete the task. If Diana works alone, she will take 5 more hours to complete the complete the task, then if she worked with Dave to complete the task? What is the ratio of the time taken by Dave to that taken by Diana if each of them worked alone to complete the task?

A. 4 : 1

B. 2 : 1

C. 10 : 1

D. 3 : 1

E. 1 : 2

1. Let x be the time required when both work together

2. Dave's time is x+20 and Diana's time is x+5

3. 1/(x+20) + 1/(x+5) = 1/x

x=10. So the ratio is 30:15 or 2:1

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Srinivasan Vaidyaraman

Sravna Holistic Solutions

http://www.sravnatestprep.com

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