median

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rupsk: Master | Next Rank: 500 Posts; Posts: 123; Joined: Mon Feb 07, 2011 12:11 pmFollowed by: 1 member

by rupsk » Sun Aug 07, 2011 6:21 pm

is the median age at the family picnic is 50?
1. the oldest person at the picnic is 85 ND THE youngest person is 15
2. half of the group are older than jerry who is 50 years old

Need an explanation for (2) as I know (1) is not sufficient.

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sunnyjohn: Master | Next Rank: 500 Posts; Posts: 344; Joined: Mon Sep 14, 2009 5:40 amFollowed by: 3 members; Thanked: 28 times; GMAT Score:700

by sunnyjohn » Sun Aug 07, 2011 9:58 pm

IMO: option 2 is sufficient to answer the Q.

Median -
if number of terms is even.

Av of 2 central term
For example- 1,2,3,4,5,6 --> Median = (3+4)/2

if number of terms is odd.

Central term is Median.
For example- 1,2,3,4,5,6,7 --> Median = 4

2. half of the group are older than jerry who is 50 years old

As we can find out half of the group, this means number of person in group must be even, which means we need 2 terms to find out median. One term is 50 and we know the next immediate value after 50 is greater than 50.

So Median = (50 + something greater than 50)/2 = greater than 50 or NOT EQUAL TO 50

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GmatKiss: Legendary Member; Posts: 2789; Joined: Tue Jul 26, 2011 12:19 amFollowed by: 43 members; Location: Chennai, India; Thanked: 206 times; GMAT Score:640

by GmatKiss » Sun Aug 07, 2011 10:13 pm

2. half of the group are older than jerry who is 50 years old

means group is even!

consider, the group to be
1,10,30,40,50,y,52,65,66,85

we do not have the value of y, so insufficient

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gmatboost: Master | Next Rank: 500 Posts; Posts: 312; Joined: Tue Aug 02, 2011 3:16 pmFollowed by: 33 members; Location: New York City; Thanked: 130 times; GMAT Score:780

by gmatboost » Sun Aug 07, 2011 11:30 pm

I agree with SunnyJohn, even though we do not know "y," we know that it is bigger than 50. Since the median is the average of 50 and y, we can conclude that it is NOT 50.

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rupsk: Master | Next Rank: 500 Posts; Posts: 123; Joined: Mon Feb 07, 2011 12:11 pmFollowed by: 1 member

by rupsk » Mon Aug 08, 2011 6:11 am

But is there are odd number of people then even we can take quotient value and can say half of the people are greater than 50 yrs.
suppose there are 5 ppl then we can take 2 ppl greater than 50years. is not that valid?

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gmatboost: Master | Next Rank: 500 Posts; Posts: 312; Joined: Tue Aug 02, 2011 3:16 pmFollowed by: 33 members; Location: New York City; Thanked: 130 times; GMAT Score:780

by gmatboost » Mon Aug 08, 2011 6:47 am

The truth is that this kind of ambiguity would never show up on the actual test.

You wouldn't see a statement that said "half of the group are older than Jerry" because as you are pointing out, it can be interpreted in different ways, and that is never good for a test.

It would either have to say "exactly half" or say something else that made it clear that the number was even. So, I guess my opinion is that there isn't really is a correct answer to your question one way or the other.

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rupsk: Master | Next Rank: 500 Posts; Posts: 123; Joined: Mon Feb 07, 2011 12:11 pmFollowed by: 1 member

by rupsk » Mon Aug 08, 2011 6:51 am

thanks to all of those who had responded.

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