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A group of people were given 2 puzzles. 79% people solved puzzle X and

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A group of people were given 2 puzzles. 79% people solved puzzle X and  [#permalink]

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New post 26 Aug 2015, 01:28
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A group of people were given 2 puzzles. 79% people solved puzzle X and 89% people solved puzzle Y. What is the maximum and minimum percentage of people who could have solved both the puzzles?

(A) 11%, 0%
(B) 49%, 33%
(C) 68%, 57%
(D) 79%, 68%
(E) 89%, 79%

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Re: A group of people were given 2 puzzles. 79% people solved puzzle X and  [#permalink]

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New post 26 Aug 2015, 03:35
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1
The maximum and minimum are establish through what's input for the neither variable. Below,
Total = Group1 + Group2 - Both + Neither

Maximum:
100 = 79 + 89 - Both + 11, where 11 is the lesser of the two not within a group.
Both = 79

Minimum:
100 = 79 + 89 - Both + 0, in that both of them had atleast one, puzzle x or puzzle y.
Both = 68

Therefore, D 79, 68
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A group of people were given 2 puzzles. 79% people solved puzzle X and  [#permalink]

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New post 26 Aug 2015, 03:36
2
consider total 100 people.
we minimize the of people who solved only X puzzle and the of people who solved only Y. This would maximize # people who solved both.
So, X min will be (100-89) =11...(89 is #people solving Y)
Y min will be (100-79) = 21...(79 is #people solving X)

Thus, Xmin + Ymin = 32. Thus XY min(#people solving both)= 100-32, i.e 68 or 68%.


Also, to maximize the number of people solving both, we need to find # people with maximum overlap.
i.e 79 people can be the # people solving X and both. In other words, none of the people solved only X. Then, we have Xonly=0, XY=79, X=79, Y=89, Yonly= 100-79, i.e 21.

Thus, we have XY max =79%

Answer:D

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Kindly correct me if it's wrong.
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Re: A group of people were given 2 puzzles. 79% people solved puzzle X and  [#permalink]

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New post 26 Aug 2015, 05:12
4
Bunuel wrote:
A group of people were given 2 puzzles. 79% people solved puzzle X and 89% people solved puzzle Y. What is the maximum and minimum percentage of people who could have solved both the puzzles?

(A) 11%, 0%
(B) 49%, 33%
(C) 68%, 57%
(D) 79%, 68%
(E) 89%, 79%

Kudos for a correct solution.


To solve this question, we don't need any formulas. Just read the question carefully. If 79% of the people solved puzzle X and 89% solved puzzle Y, then maximum % that can solve both correctly can only be 79%. From the given options, only D looks good

Answer D
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A group of people were given 2 puzzles. 79% people solved puzzle X and  [#permalink]

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New post 26 Aug 2015, 20:09
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1
Overlapping Sets formulas
Formula 1: Total = X total + Y total - Both + Neither
Formula 2: Total = X only + Y only + Both + Neither

You are given that
100 = 79 + 89 - Both + Neither


Maximum "Both"
Total = X only + Y only + Both + Neither
100 = 0 + 79 + 10 + 11

Minimum "Both"
Total = X only + Y only + Both + Neither
100 = 11 + 68 + 21 + 0

Hence, option D (79, 68)
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Re: A group of people were given 2 puzzles. 79% people solved puzzle X and  [#permalink]

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New post 27 Aug 2015, 06:08
2
Bunuel wrote:
A group of people were given 2 puzzles. 79% people solved puzzle X and 89% people solved puzzle Y. What is the maximum and minimum percentage of people who could have solved both the puzzles?

(A) 11%, 0%
(B) 49%, 33%
(C) 68%, 57%
(D) 79%, 68%
(E) 89%, 79%

Kudos for a correct solution.


IMO : D

Max Overlap we can obtain from two values i.e. 79 and 89 will be 79.
Only Option D has Max = 79.
Thus We need not calculate the min. value
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Re: A group of people were given 2 puzzles. 79% people solved puzzle X and  [#permalink]

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New post 30 Aug 2015, 08:49
2
Bunuel wrote:
A group of people were given 2 puzzles. 79% people solved puzzle X and 89% people solved puzzle Y. What is the maximum and minimum percentage of people who could have solved both the puzzles?

(A) 11%, 0%
(B) 49%, 33%
(C) 68%, 57%
(D) 79%, 68%
(E) 89%, 79%

Kudos for a correct solution.


VERITAS PREP OFFICIAL SOLUTION:

The first thing to note here is that we do not know the % of people who could not solve either puzzle. All we know is that puzzle X was solved by 79% of the people and puzzle Y was solved by 89% of the people.

Image

Let’s first try to maximize the % of people who solved both the puzzles. We want to make these two sets overlap as much as possible i.e. we need to get them as close to each other as possible. Region of overlap can be 79% at most since we know that only 79% people solved puzzle X. In this case, the venn diagram will look something like this.

Image

Hence, the maximum % of people who could have solved both the puzzles is 79%.

Now, let’s try to minimize the % of people who solved both the puzzles. We want the sets to be as far apart as possible. In this case, the % of people who solved neither puzzle must be 0. Only then will the overlap of the sets be as little as possible.

Image

In this case, 68% people must have solved both the puzzles.

Hence, the answer is (D)
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New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
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Re: A group of people were given 2 puzzles. 79% people solved puzzle X and  [#permalink]

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New post 13 Jan 2018, 06:33
2 puzzles: X & Y.
Let x be the the no. of people who solved both.
100= (79+89) - x + neither (=> taking the component of neither is key here)

lets try to express x as f(neither)

x= 68 + neither
Now neither can takes values of 0 till (100-89)
min: x= 68+0 =68
max: x= 68+11 =79
Re: A group of people were given 2 puzzles. 79% people solved puzzle X and &nbs [#permalink] 13 Jan 2018, 06:33
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