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Hi! Would anyone be able to help with this tough question from gmac mock 5?
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This is a lovely answer. Thank you
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unicornilove
Hi! Would anyone be able to help with this tough question from gmac mock 5?
Let X be the number of employees that joined all two committees. Let Y be the number of employees that joined three committees.

Recall the formula for number of unique elements:
(Total # in A) + (Total # in B) + (Total # in C) - (# in groups of exactly 2) - 2*(# in groups of exactly 3) + (# in neither)

Applying this formula,
40+40+40-X-2(Y)+0=110

To solve for min and max,
(1) Assume X=0, 120-0-2(Y)=110
Y=5
(2) Assume Y=0, 120-X-2(0)=110
X=10

Therefore, Min is 5, Max is 10

Posted from my mobile device
­
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Would you like to discuss this question?

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chetan2u  The highlighted part was not completely clear to me. Will you be kind enough to  exemplify it and  break it down for me a bit ? 
Quote:

unicornilove
­A certain company has the following policy regarding membership in committees A, B, C: each of the committees have exactly 40 members, and each employee must be a member of at least one of the committees. The company currently has 110 employees. 

Let X be the current number of employees who are members of more than one of the committees. Based on the current total number of employees, select the least value of X that is compatible with the policy and select the greatest value of X that is compatible with the policy. ­
Short and simple..

If each employee was part of exactly one company, then total employee would have been 40+40+40 or 120. But there are 110 employees, so these 10 extra, 120-110, must get adjusted in employees being part of more than one company.

Least value of X: This would happen when the extra are adjusted in the overlap area of all three companies, that is the individual is part of all three companies. So each individual would account for 3 employees, one each in A, B and C. Thereby, that employ is accounting for two more employees.
If 2 employees are catered for by one employee, then 10 employees will get catered by 10/2 or 5 employees.


Maximum value of X: This would happen when the extra are adjusted in the overlap area of exactly two companies, that is the individual is part of only two companies. So each individual would account for 2 employees, one each in A and B or A and C or B and C. Thereby, that employ is accounting for one more employee.
If 1 employee is catered for by one employee, then 10 employees will get catered by 10/1 or 10 employees.
­
­
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chetan2u  The highlighted part was not completely clear to me. Will you be kind enough to  exemplify it and  break it down for me a bit ? 
Quote:

unicornilove
­A certain company has the following policy regarding membership in committees A, B, C: each of the committees have exactly 40 members, and each employee must be a member of at least one of the committees. The company currently has 110 employees. 

Let X be the current number of employees who are members of more than one of the committees. Based on the current total number of employees, select the least value of X that is compatible with the policy and select the greatest value of X that is compatible with the policy. ­
Short and simple..

If each employee was part of exactly one company, then total employee would have been 40+40+40 or 120. But there are 110 employees, so these 10 extra, 120-110, must get adjusted in employees being part of more than one company.

Least value of X: This would happen when the extra are adjusted in the overlap area of all three companies, that is the individual is part of all three companies. So each individual would account for 3 employees, one each in A, B and C. Thereby, that employ is accounting for two more employees.
If 2 employees are catered for by one employee, then 10 employees will get catered by 10/2 or 5 employees.


Maximum value of X: This would happen when the extra are adjusted in the overlap area of exactly two companies, that is the individual is part of only two companies. So each individual would account for 2 employees, one each in A and B or A and C or B and C. Thereby, that employ is accounting for one more employee.
If 1 employee is catered for by one employee, then 10 employees will get catered by 10/1 or 10 employees.
­
­
­Say there was one employee each in sections A, B and C of company X, but the total number of employee in X was only one.

How would that happen: It would be possible only when the same employee is part of the three sections. Here, three(1+1+1) employees in total in A, B and C is catered by just one employee in the overlap region 'All three'. So, this one employee in X accounts for the increase 3-1 or 2 employee. 
Relate it to a Venn Diagram and the overlapping Zone and it will be easier to comprehend.
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HeyBarbie

unicornilove
Hi! Would anyone be able to help with this tough question from gmac mock 5?
Let X be the number of employees that joined all two committees. Let Y be the number of employees that joined three committees.

Recall the formula for number of unique elements:
(Total # in A) + (Total # in B) + (Total # in C) - (# in groups of exactly 2) - 2*(# in groups of exactly 3) + (# in neither)

Applying this formula,
40+40+40-X-2(Y)+0=110

To solve for min and max,
(1) Assume X=0, 120-0-2(Y)=110
Y=5
(2) Assume Y=0, 120-X-2(0)=110
X=10

Therefore, Min is 5, Max is 10

Posted from my mobile device
­This is a great solution   :clap: 
I had gone by the options (if not approaching the unique elements) and this is how I solved it.

Firstly, we have to understand that members can be common either in all 3 groups or in 2 groups.

If they are common in all 3 groups, then naturally the number of members overall will be less. Let's check the options.
If the number of common members is 3, then 3+((40-3)*3)=114. Wrong.
If the number of common members is 5, then 5+((40-5)*3)=110. Correct.
You can similarly calculate for other options, none will fit.

Let's now find the greatest number of overall members. Here, common members will be present in 2 groups.
If the number of common members is 3, then 3+((40-3)*2)+40=117. Wrong.
If the number of common members is 5, then 5+((40-5)*2)+40=115. Wrong.
If the number of common members is 10, then 10+((40-10)*2)+40=110. Correct
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HeyBarbie chetan2u Thanks a lot for the solutions!
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Have a logical doubt:

When we have three groups, A, B, and C, and want to minimise the total number of people in two or more of those groups.

Let's say out of 110 people, 40 are a part of group A, leaving us with 110-40=70 members in total in the group unassigned.

Now, we assign B to 40 out of the remaining 70, which leaves us with 70-40=30.

Now, to assign C to at least 40 out of the remaining 30, we can assign it to the remaining 30 people who are unassigned, which would leave us with 10 yet to be assigned.

And since all the people have been assigned to Group A, B, or C, we can minimise the total number by having these 10 people already assigned to A/B and assigned to C.

Therefore, Min Value should be 10.


This is the approach I used to solve, prevalent among set problems with least/greatest intersection value. Can anyone help understand where I went wrong?

KarishmaB Bunuel
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kabirgandhi
Have a logical doubt:

When we have three groups, A, B, and C, and want to minimise the total number of people in two or more of those groups.

Let's say out of 110 people, 40 are a part of group A, leaving us with 110-40=70 members in total in the group unassigned.

Now, we assign B to 40 out of the remaining 70, which leaves us with 70-40=30.

Now, to assign C to at least 40 out of the remaining 30, we can assign it to the remaining 30 people who are unassigned, which would leave us with 10 yet to be assigned.

And since all the people have been assigned to Group A, B, or C, we can minimise the total number by having these 10 people already assigned to A/B and assigned to C.

Therefore, Min Value should be 10.


This is the approach I used to solve, prevalent among set problems with least/greatest intersection value. Can anyone help understand where I went wrong?

KarishmaB Bunuel


Nothing wrong with that but we are not taking overlap of all 3 in that case. If only overlap of 2 is allowed then 10 people must be in the overlap region since None = 0.

But when all 3 overlap is also allowed, we can reduce the number of people in the overlap region. Think in terms of instances and people. We have 110 people and 120 instances. We can distribute 110 instances to 110 people - one each since everyone should be on at least one committee. Now 10 instances are remaining to be distributed. You can give one each to 10 people or 2 each to 5 people. So minimum overlap is 5 and maximum is 10.
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in the question, X is number of employees in more than one committee. So employees who joined 2 committees and 3 committees, right? in the formula, do we need to multiply by 2?
HeyBarbie
unicornilove
Hi! Would anyone be able to help with this tough question from gmac mock 5?

Let X be the number of employees that joined all two committees. Let Y be the number of employees that joined three committees.

Recall the formula for number of unique elements:
(Total # in A) + (Total # in B) + (Total # in C) - (# in groups of exactly 2) - 2*(# in groups of exactly 3) + (# in neither)

Applying this formula,
40+40+40-X-2(Y)+0=110

To solve for min and max,
(1) Assume X=0, 120-0-2(Y)=110
Y=5
(2) Assume Y=0, 120-X-2(0)=110
X=10

Therefore, Min is 5, Max is 10

Posted from my mobile device
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When finding the maximum value of X we use 2 because it allows the maximum amount of people to be in 2 or more committees. We multiply by 3 when we are looking for the minimum amount of people in 2 or more committees.
Ak284
in the question, X is number of employees in more than one committee. So employees who joined 2 committees and 3 committees, right? in the formula, do we need to multiply by 2?
HeyBarbie
unicornilove
Hi! Would anyone be able to help with this tough question from gmac mock 5?

Let X be the number of employees that joined all two committees. Let Y be the number of employees that joined three committees.

Recall the formula for number of unique elements:
(Total # in A) + (Total # in B) + (Total # in C) - (# in groups of exactly 2) - 2*(# in groups of exactly 3) + (# in neither)

Applying this formula,
40+40+40-X-2(Y)+0=110

To solve for min and max,
(1) Assume X=0, 120-0-2(Y)=110
Y=5
(2) Assume Y=0, 120-X-2(0)=110
X=10

Therefore, Min is 5, Max is 10

Posted from my mobile device
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