Pecan Trees

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justharsha: Senior | Next Rank: 100 Posts; Posts: 44; Joined: Fri Apr 20, 2012 1:02 pm

by justharsha » Sun Nov 24, 2013 7:16 pm

If a certain grove consists of 36 pecan trees, what was the yield per tree last year?
(1) The yield per tree for the 18 trees in the northern half of the grove was 60 kilograms last year.
(2) The yield per tree for the 18 trees in the eastern half of the grove was 55 kilograms last year.

[spoiler]OA: E.
I would think it would be C since there is a total of 36 trees as mentioned in the Question
[/spoiler]

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Source: Beat The GMAT — Data Sufficiency | Sun Nov 24, 2013 7:16 pm

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by [email protected] » Sun Nov 24, 2013 8:01 pm

Hi justharsha,

I just answered this DS question in another post; here is the explanation...

Sometimes DS questions don't give you a sense of what you need to know until you read the 2 Facts.

We're told that a grove has 36 trees in it and we're asked what the yield/tree was last year? This question implies that we'll be using the average formula.

Fact 1: The yield/tree for the 18 trees in the northern half of the grove was 60 kg.

This means that the TOTAL yield for the NORTH half was 18x60 = 1080kg. However, we don't know what the yield was for the SOUTH half of the grove.
Fact 1 is INSUFFICIENT.

Fact 2: The yield/tree for the 18 trees in the eastern half of the grove was 55 kg.

This means that the TOTAL yield for the EAST half was 18x55 = 990kg. However, we don't know what the yield was for the WEST half of the grove.
Fact 2 is INSUFFICIENT.

Combined, we know that the grove can be broken down into North & South and East and West, but we don't know how many trees are in each subcategory (how many are in the Northwest, for example). Without THAT specific information, there's no way to figure out the overall average.

Final Answer: E

GMAT assassins aren't born, they're made,
Rich

Contact Rich at [email protected]

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Uva@90: Master | Next Rank: 500 Posts; Posts: 490; Joined: Thu Jul 04, 2013 7:30 amFollowed by: 5 members; Location: Chennai, India; Thanked: 83 times

by Uva@90 » Sun Nov 24, 2013 8:11 pm

[email protected] wrote:Hi justharsha,

I just answered this DS question in another post; here is the explanation...

Sometimes DS questions don't give you a sense of what you need to know until you read the 2 Facts.

We're told that a grove has 36 trees in it and we're asked what the yield/tree was last year? This question implies that we'll be using the average formula.

Fact 1: The yield/tree for the 18 trees in the northern half of the grove was 60 kg.

This means that the TOTAL yield for the NORTH half was 18x60 = 1080kg. However, we don't know what the yield was for the SOUTH half of the grove.
Fact 1 is INSUFFICIENT.

Fact 2: The yield/tree for the 18 trees in the eastern half of the grove was 55 kg.

This means that the TOTAL yield for the EAST half was 18x55 = 990kg. However, we don't know what the yield was for the WEST half of the grove.
Fact 2 is INSUFFICIENT.

Combined, we know that the grove can be broken down into North & South and East and West, but we don't know how many trees are in each subcategory (how many are in the Northwest, for example). Without THAT specific information, there's no way to figure out the overall average.

Final Answer: E

GMAT assassins aren't born, they're made,
Rich

Rich,
Will GMAT test these kind of questions ?
I am seriously scared. If they play with words. I will be gone..

Regards,
Uva.

Known is a drop Unknown is an Ocean

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justharsha: Senior | Next Rank: 100 Posts; Posts: 44; Joined: Fri Apr 20, 2012 1:02 pm

by justharsha » Mon Nov 25, 2013 10:06 am

Thanks for the response Rich but why should we be making the assumption that trees were planted with the South, West, NW etc.
Is it not possible that the trees were planted only in the North and East? This will give us the total of 36 trees as mentioned in the Question. Isnt the assumption an added information by the reader?

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[email protected]: Elite Legendary Member; Posts: 10392; Joined: Sun Jun 23, 2013 6:38 pmFollowed by: 511 members; Location: Palo Alto, CA; Thanked: 2867 times; GMAT Score:800

by [email protected] » Mon Nov 25, 2013 3:01 pm

Hi Uva,

YES, the GMAT will ask you a few DS questions that are more about logical reasoning than about math. Don't be afraid of these questions; they're normally straight-forward enough that you can think your way past them. Drawing a picture might help. Think about what you KNOW and what you DON'T KNOW and you'll have the correct answer fairly quickly.

Hi justharsha,

We can make THOSE assumptions because the information in the two Facts essentially tells us to. We're told that there are 36 trees. Fact 1 tells us that 18 of the trees were in the northern HALF of the grove. So where were the other 18? The southern HALF. Fact 2 tells us that 18 trees were in the eastern HALF. So where were the other 18? In the western HALF.

GMAT assassins aren't born, they're made,
Rich

Contact Rich at [email protected]

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