Problems with Work/Rate questions

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Problems with Work/Rate questions [#permalink]

07 Apr 2011, 10:36

Hi guys, I’m having tremendous problems studying for rate and work questions... I’ve been studying for around 8 months... and have been able to spin around these questions but know I need to absolutely know them..
I have read the rate/Work section in the MGMAT words translations,, but It only helped me on rates.. speed etc... cars moving towards and away... but in work questions I am a mess. Im doing rate and work questions here on the gmatclub.com forums.... the rate questions I know im getting the jist of them... but I can hardly do any work questions.... I am in serious trouble on this... I cant afford to get a very simple work problem in the first 1-10 question ...

Can anyone recommend me a way to study the work questions?? apart from the words trnslations.. it only covers very little the work problems..

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Re: Problems with Work/Rate questions [#permalink]

09 Apr 2011, 15:59

1) Use unitary method for simple problems
e.g If A can complete a unit of work in 10 days, how many days can A do two units of work working at half the efficiency?
1 unit in 10 days
2 units in x days
i.e. x = 20
with full efficiency - 20 days
with 1/2 efficiency - y days
so logically, it should be double the time i.e. 40 days

2) Slightly complex problems - use
(1/x + 1/y = 1/Time) Below example explains how this formula can be derived.

e.g. If A can do something in 3 hours and B can do the same in 2, how long would it take them while working together?
A can do 1 unit in 3 hours
A can do x units in 1 hours
So x = 1/3

Similarly, B can do 1 unit in 2 hours
B can do y units in 1 hours
So y = 1/2

In one hour, total work = work done by A + work done by B
i.e. 1/3 + 1/2
=> 5/6

Again, unitary method
5/6th work can be done in 1 hour
1 work (i.e. full) can be done in x hours
i.e. x = 6/5

Instead of using this method, just plug in the values in the formula.
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Re: Problems with Work/Rate questions [#permalink]

09 Apr 2011, 20:33

You should practice word translations and word problems. Practice moving from words to equations and from equations to words.

MGMAT and Veritas both have a book on this subject.

MGMAT:
http://www.amazon.com/Word-Translations ... =8-1-spell
MGMAT ebook:
http://www.amazon.com/Translations-Prep ... =8-2-spell

Veritas:
http://www.veritasprep.com/gmat-prep-books/
(the individual Veritas book is not available on Amazon)
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Re: Problems with Work/Rate questions [#permalink] 09 Apr 2011, 20:33

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Problems with Work/Rate questions

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