woohoo921 wrote:
ReedArnoldMPREP wrote:
There are 20 cookies to start with. Every hour, Etienne eats 20 cookies, and Jacque cooks 16 more. That's a net loss of 4 cookies every hour.
So after one hour, there are 16 cookies, after two hours, 12 cookies, until after five hours, there are no cookies left.
Algebraically:
20 - 20x + 16x = cookies left.
20 - 4x = cookies left.
How long until 0 cookies left?
20 - 4x = 0
So 20 = 4x
So 5 = x.
ReedArnoldMPREPI noticed that the answer key from MP says "Note that Etienne eats a lot more than 20 cookies. In 5 hours he eats 100 cookies—the initial 20, plus the 80 that Jacques makes in that 5 hours." I am a bit confused as to why we set the work = 20 cookies then.
The '20' in the equation isn't 'work.' The whole equation is not a 'W=RT' equation. It's a 'cookies left' equation. 20 is the original number of cookies. So the equation is:
[Original number of cookies] - [Number of cookies Etienne eats in 'x' hours] + [Number of cookies Jacques bakes in x hours] = [# of cookies remaining]
The number of cookies Etienne eats can be thought of as a 'W=RT' equation: [# cookies eaten = cookies eaten per hour * number of hours = 20x]
The number of cookies Jacques bakes can be 'W=RT' as well: [# cookies baked = cookies baked per hour * number of hours = 16x]
So we end up with:
20 - 20x + 16x = 'cookies remaining'
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REED ARNOLDManhattan Prep GMAT InstructorVideo: The 24 Things Every GMAT Studier Needs to DoHow to Improve a GMAT ScoreThe Studying Verbal Starter Kit (...That's much more than a 'starter kit')The Studying Quant Starter Kit (...That's much more than a 'starter kit')The PERFECT data sufficiency question:On a three person bench, George sits in the middle of Alice and Darryl. If Alice is married, is an unmarried person sitting next to a married person?
1). George is married.
2). Darryl is not married.
Answer: