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 Post subject: Work ProblemPosted: Sun Nov 13, 2011 4:02 pm

Joined: Sun Oct 30, 2011 8:08 pm
Posts: 3
I have attached a link to the website and a jpeg as well

I need help with question #8

http://www.kutasoftware.com/FreeWorkshe ... oblems.pdf

 Attachments: Work Prob 8.jpg [ 254.96 KB | Viewed 1681 times ]
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 Post subject: Re: Work ProblemPosted: Mon Nov 14, 2011 5:06 pm

Joined: Thu Jul 03, 2008 2:13 pm
Posts: 117
Hey CB34,

Good question - and kudos on seeking out additional rate problem practice!

Here's one example where the skills covered are GMAT-relevant but the numbers really aren't. The GMAT is great at picking numbers that allow for pretty convenient calculation if you perform the algebra well, and it's also great because it provides answer choices that you could use if the math ever gets cumbersome.

For the rate problem setup... When two people/machines are working together to complete a job, you can add the rates together, and that's a great step to take in this one.

Kristin's rate is 1 field / 11 hours, and Kayla's is 1 field / 16 hours. We can add those together:

1/11 + 1/16 = combined rate (in fields per hour)

What's ugly here is that there aren't any commonalities to the denominators so the math gets a little ugly:

1/11 = 16/176 and 1/16 = 11/176 (176 = 11*16, so that's your common denominator)

16/176 + 11/176 = 27/176

So your combined rate is 27/176, and we want to use that rate to solve for the amount of time it will take to harvest one field:

27/176 = 1 field / x hours

x(27/176) = 1
x = 176/27

Again, the GMAT would have answer choices here so you wouldn't have to do the long division. You could estimate this one to be near 180/30, which is 6, but the pure math breaks out to around 6.5.

NOW...the math is a little messy, and what's nice about GMAT problems is that the answer choices often save you from a lot of that. We know that, on her own, Kristin does 1 field in 11 hours. If we added one more Kristin, we'd just halve the time to 5.5. But Kayla is slower, so we need something a little longer than 5.5 hours to account for Kayla's slightly-slower speed. So if there were answer choices, you'd be looking for something around 6 or a little higher, and you might be able to get to 6.5-ish without actually doing the math...

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 Post subject: Re: Work ProblemPosted: Tue Nov 15, 2011 12:28 am

Joined: Sun Oct 30, 2011 8:08 pm
Posts: 3
Thank you, this was very helpful. Sometimes, I get stuck on the small stuff like division after working on several drills. I literally didn't divide properly and thought I did the problem wrong, lol Next time ill be sure check my answer.

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