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Grockit blog DS

by GmatKiss » Sat Oct 15, 2011 7:05 am
From Grockit blog,
https://grockit.com/blog/gmat/category/g ... fficiency/

Mrs. K's class has 10 students. If the average age of the students is 12, then how many of the students are 12 years of age?

(1) None of the students are younger than 12.

(2) None of the students are older than 12.

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient to answer the question asked, and additional data are needed.

Even if we don't know the answer, we can see that if 1 is sufficient, then 2 must also be sufficient. Answer choices (A) and (B) are eliminated. Means always must be somewhere between the extremes, so if there are no values below 12, then ALL the values must equal 12. Choice (D) is the answer.

Is it not C?!
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by parul9 » Sat Oct 15, 2011 7:26 am
Class K has 10 students.
The avg age is 12.
Asked: How many students have age = 12.

statement 1 : None of the students are younger than 12.
So all the students will have age 12. Ans 10, sufficient.

Statement 2 : None of the students are older than 12.
So, all students will have age 12. Ans 10, sufficient.

So, we can get the answer by EACH statement ALONE.
So answer is D.
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by sam2304 » Sat Oct 15, 2011 7:32 am
GmatKiss wrote: Mrs. K's class has 10 students. If the average age of the students is 12, then how many of the students are 12 years of age?

(1) None of the students are younger than 12.

(2) None of the students are older than 12.
Average age is 12
1. If one or more students > 12 years average would be more than 12
say 9 ppl 12 years and one person 14 years then its 122/10 = 12.2
2. If one or more students < 12 years average would be less than 12
say 9 people 12 years and one person 10 years then its 118/10 = 11.8

So D.
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by sl750 » Sat Oct 15, 2011 8:24 am
IMO D
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by saketk » Tue Oct 18, 2011 2:14 am
GmatKiss wrote:From Grockit blog,
https://grockit.com/blog/gmat/category/g ... fficiency/

Mrs. K's class has 10 students. If the average age of the students is 12, then how many of the students are 12 years of age?

(1) None of the students are younger than 12.

(2) None of the students are older than 12.

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient to answer the question asked, and additional data are needed.
Hi -- Answer cannot be C for the following reason..

stmt 1: -- says none of the students are younger than 12 yrs of age.

That means the minimum age = 12. If we equally divide the age then 10 students will each be of 12 yrs of age.

if we try to make even one of them = 13 then someone's age will go below 12, which is not allowed.

hence this condition is sufficient.

Similar logic can be applied to stmt 2 as well.

Hence both the stmts are sufficient.

OPTION D
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