DATA Sufficiency - Data Sufficiency Questions and Answers - Data Sufficiency Practice Questions

DATA Sufficiency - Data Sufficiency Questions and Answers - Data Sufficiency Practice Questions, Data sufficiency does not have to be hard, but you do have to focus on three things

1. What you know
2. What you need to know
3. what the real question is

What do I know? There are 2 sections with 84 total students. There are male students & female students

What is the question? How many total female students are there? 

What do I need to know? I need to know 2 things… (1) The total number of people in each sections & (2) The % of female students in each section. 

I always create (AD/BCE). So, I start with #1

 (1) ⅔ of students in section 1 are female.

Right away, we know this is insufficient because we don’t know anything about section 2. Eliminate AD

(2) ½ of students in section 2 are male.

Again, you fall into the same trap as (1). Knowing about section 2 means nothing if we know nothing about section 1. Eliminate B 

We are left with C & E.

 (1,2) We now know that ⅔ of section 1 is female & ½ of section 2 is female. That would, initially, sound right. But upon further examination, we know that we need to find both the % and the total in each section. See, we don’t know how many people are in section 1. If there are 3 people we get a different answer if there are 60 people. Eliminate C

 Pick E

*NOTE* This is a Value DS problem. We used knowledge about “unknowns” to eliminate the answer choices. In terms of math, this is how ratios relate to real numbers. Typically, if they give you ratios, you need to be on alert for the real number those ratios relate to.

Question #2

What is the average of j and k?

1. The average of j + 2 and k + 4 is 11.

2. The average of j, k, and 14 is 10.

*NOTE: On Average DS problems, you need to remember that there are three elements (the sum, the number of things, and the average) Every time you do them, make sure you know which element you are looking for and which elements you are given*

Three things, as always:

1. What do I know?
2. What is the question?
3. What do I need to know?

I know that there are three things… the sum of J&K… the average… and the number of things.

 So, (j+k)/2 = average

Or, j+k = 2(average)

I need to find the average, so really, I need to find the sum of j & k

Goal: (j+k)

(1) J+2 + k + 4 / 2 == 11, OR j + k + 2 + 4 == 22, or j + k == 16... SUFFICIENT

Because we can work backwards & find out what (j+k) is, we can solve this. Keep AD, eliminate BCE.