stats

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ricaototti: Junior | Next Rank: 30 Posts; Posts: 29; Joined: Wed Feb 27, 2008 4:56 am; Thanked: 2 times

by ricaototti » Thu Sep 04, 2008 9:33 pm

If set S = {7, y, 12, 8, x, 9}, is x + y less than 18?

(1) The range of set S is less than 9.

(2) The average of x and y is less than the average of set S.

OA b

But I dont get the reasoning. I would like to have a step by step explanation of why B is correct.

What I did for B: I just plugged in a few numbers.That is what I usually do when I dont have a quick nice approach to tackle the question. Should I change this strategy? It doesnt always work out all right...

How many questions on Stats in the real GMAT? By stats I mean what includes mean, range, std, median....

THANKS

Source: Beat The GMAT — Data Sufficiency | Thu Sep 04, 2008 9:33 pm

parallel_chase: Legendary Member; Posts: 1153; Joined: Wed Jun 20, 2007 6:21 amFollowed by: 2 members; Thanked: 146 times

Re: stats

by parallel_chase » Fri Sep 05, 2008 2:36 am

ricaototti wrote:If set S = {7, y, 12, 8, x, 9}, is x + y less than 18?

(1) The range of set S is less than 9.

(2) The average of x and y is less than the average of set S.

OA b

But I dont get the reasoning. I would like to have a step by step explanation of why B is correct.

What I did for B: I just plugged in a few numbers.That is what I usually do when I dont have a quick nice approach to tackle the question. Should I change this strategy? It doesnt always work out all right...

How many questions on Stats in the real GMAT? By stats I mean what includes mean, range, std, median....

THANKS

Statement I

range of the set is less than 9, x could be anything and y could be anything.

x+y can be less than 18, x+y can be more than 18.

Insufficient.

Statement II

(x+y)/2 < (36+x+y)/6

(x+y)/2 < 6 + (x+y)/6

x+y < 12 + (x+y)/3

If you insert values for x and y, you will notice that x+y will always be less than 18 to satisfy the above equation.

Answer is no.
Hence Sufficient.

Answer is B.

You can see anywhere between 2-3 questions on stats, but it could be more or it could be less on the actual GMAT.

Hope this helps.

mayur00: Senior | Next Rank: 100 Posts; Posts: 35; Joined: Mon Jun 23, 2008 1:41 pm; Thanked: 2 times

by mayur00 » Fri Sep 05, 2008 9:40 am

I think ricaototti's solutions is correct.

However, you can further simplify
(x+y)/2 < (36+x+y)/6

to give x+y<18

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