Data Sufficiency

I thought I'd point out that Mitch's "group grid" approach (aka Double Matrix Method) is a must-have skill for the GMAT, since these kinds of overlapping sets questions are VERY common on the GMAT. In fact, I'll go as far as saying that it's likely that you'll encounter at least one of them on test day.

We can use this technique for most questions featuring a population in which each member has two characteristics associated with it.
Here, we have a population of companies, and the two characteristics are:
- requires computer skills OR does not require computer skills.
- requires writing skills OR does not require writing skills

To learn more about the Double Matrix Method, watch our free video: https://www.gmatprepnow.com/module/gmat- ... ems?id=919

Once you're familiar with this technique, you can attempt these additional practice questions:

Easy Problem Solving questions
- https://www.beatthegmat.com/the-aam-aad ... 72242.html
- https://www.beatthegmat.com/finance-maj ... 67425.html

Medium Problem Solving questions
- https://www.beatthegmat.com/probability ... 73360.html
- https://www.beatthegmat.com/posted-spee ... 72374.html
- https://www.beatthegmat.com/motel-t271938.html
- https://www.beatthegmat.com/of-the-appl ... 70255.html
- https://www.beatthegmat.com/opening-nig ... 64869.html
- https://www.beatthegmat.com/ds-french-j ... 22297.html

Difficult Problem Solving questions
- https://www.beatthegmat.com/ratio-problem-t268339.html
- https://www.beatthegmat.com/overlapping ... 65223.html
- https://www.beatthegmat.com/fractions-t264254.html
- https://www.beatthegmat.com/overlapping ... 64092.html
- https://www.beatthegmat.com/mba/2011/05 ... question-2

Easy Data Sufficiency questions
- https://www.beatthegmat.com/for-what-pe ... 70596.html
- https://www.beatthegmat.com/ds-quest-t187706.html

Medium Data Sufficiency questions
- https://www.beatthegmat.com/sets-matrix-ds-t271914.html
- https://www.beatthegmat.com/each-of-peo ... 71375.html
- https://www.beatthegmat.com/a-manufacturer-t270331.html
- https://www.beatthegmat.com/in-costume- ... 69355.html
- https://www.beatthegmat.com/mba/2011/05 ... question-1

Difficult Data Sufficiency questions
- https://www.beatthegmat.com/double-set- ... 71423.html
- https://www.beatthegmat.com/sets-t269449.html
- https://www.beatthegmat.com/mba/2011/05 ... question-3

Cheers,
Brent

prernamalhotra wrote:Of the companies surveyed about the skills they required in prospective employees, 20% required both computer skills and writing skills. What percent of companies surveyed required neither computer skills nor writing skills?

A) Of those companies surveyed that required computer skills, half required writing skills
B) 45% of the companies surveyed required writing skills but not computer skills

We can use the formula:

Total = Computer + Writing - Both + Neither

So in terms of percentage, we have:

100 = Computer + Writing - 20 + Neither

120 = Computer + Writing + Neither

We need to determine Neither, so we need to know Computer and Writing.

Statement One Only:

Of those companies surveyed that required computer skills, half required writing skills.

This means computer skills must be 40 since half of it is 20, which is both computer and writing skills. Therefore, we have:

120 = 40 + Writing + Neither

However, without knowing the value of Writing, we can't determine Neither. Statement one alone is not sufficient.

Statement Two Only:

45% of the companies surveyed required writing skills but not computer skills.

Notice writing skills only = Writing - Both, so 45 = Writing - 20 or Writing = 65. So we have:

120 = Computer + 65 + Neither

However, without knowing the value of Computer, we can't determine Neither. Statement two alone is not sufficient.

Statements One and Two Together:

With both statements, we have:

120 = 40 + 65 + Neither

15 = Neither

Answer: C