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sxjain3: Junior | Next Rank: 30 Posts; Posts: 12; Joined: Thu Mar 20, 2008 5:23 am; Location: USA; Thanked: 1 times

DS Question - Not agreeing with the answer

by sxjain3 » Sat May 24, 2008 3:52 pm

This is a question from the DS list of questions in the Word document

Sectio 14 / Question - 10 -

If the average (arithmetic mean) of six numbers is 75, how many of the numbers are equal to 75 ?

(1) None of the six numbers is less than 75.
(2) None of the six numbers is greater than 75.

The answer provided is : C

But I get "d"

Thoughts ?

Last edited by sxjain3 on Sat May 24, 2008 5:03 pm, edited 1 time in total.

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Source: Beat The GMAT — Data Sufficiency | Sat May 24, 2008 3:52 pm

netigen: Legendary Member; Posts: 631; Joined: Mon Feb 18, 2008 11:57 pm; Thanked: 29 times; Followed by:3 members

by netigen » Sat May 24, 2008 4:04 pm

Shouldn't the answer be D

(a) >=75 so all of them are 75 otherwise the avg can not be 75
(b) <=75 so all of them are 75 otherwise the avg can not be 75

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luvaduva: Senior | Next Rank: 100 Posts; Posts: 84; Joined: Tue Feb 05, 2008 8:52 pm; Thanked: 8 times

by luvaduva » Sat May 24, 2008 4:13 pm

I get (D)

The stem tells us the mean is 75.

75 = sum/6, So, the sum must equal 75*6 = 450 *both statements say n=6*

(1) The only way for this statement to be true(which statements are ALWAYS TRUE) is for each number to be 75.

(2) Same applies to this.

You can spend some time on this and set up an equation if you like:

For (1):

(75+a) + (75+b) + (75+c) + (75+d) + (75+e) + (75+f) = 450

75*6 + (a+b+c+d+e+f) = 450
450 + (a+b+c+d+e+f) = 450
(a+b+c+d+e+f) = 0

The same applies to for (2) except it would be: 75 -a ...