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At Rocket Brown Elementary School, there are 150 students and three sports teams – hockey, tennis, and football. Rocket Brown students are allowed to participate in as many of the three sports as they like or to abstain from participation completely, and every student who chooses a team must make that team. At the beginning of the semester, 40 students choose to play on the hockey team, 50 choose to join the tennis team, 90 choose to play on the football team, and 70 students decide to play exactly two sports simultaneously.

In the table, select a value for the greatest possible number of students who could choose to play all three sports and a value for the greatest possible number of students who could choose to play no sports at all. Make only two selections, one in each column.

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chetan2u
­At Rocket Brown Elementary School there are 150 students and three sports teams – hockey, tennis, and football. Rocket Brown students are allowed to participate in as many of the three sports as they like or to abstain from participation completely. At the beginning of the semester, 40 students choose to play hockey, 50 choose to play tennis and 90 choose to play football, while 70 decide to play exactly two sports simultaneously.

In the table, select a value that would be the greatest number of students who could choose to play all three sports and the greatest number of students who could choose to play no sports at all. Make only two selections, one in each column.­
­With 96% incorrect out of first 24 timers taken, the question may seem to be very tough, but can be simplified by Venn Diagram.

Otherwise, the solution would be 

Different components: Only h, Only t, Only f, Only h&t, Only h&f, Only t&f, all three, None

Given:
Total = Only h + Only t + Only f + Only h&t + Only h&f + Only t&f+ all three + None  = 150
H = Only h + Only h&t + Only h&f + all three = 40
T = Only t + Only h&t + Only t&f + all three = 50
F = Only f + Only f&t + Only h&f + all three = 90
Only h&t + Only h&f + Only t&f = 70

So, just re arranging the total....
H+T+F=40+50+90 = 180
(Only h + Only h&t + Only h&f + all three) + (Only t + Only h&t + Only t&f + all three) + (Only f + Only f&t + Only h&f + all three) = 180
Only h + Only t + Only f + 2(Only h&t + Only h&f + Only t&f) + 3(all three)  = 180
(Only h + Only t + Only f + Only h&t + Only h&f + Only t&f + all three) + (Only h&t + Only h&f + Only t&f) + 2*all three  = 180
(150 - None) + 70 + 2*all three = 180
 None - 2* all three = 40

As we increase None, 'all three will also increase'. Thus, for All \(three_{max}\), we will get \(None_{max}\)
As 90 play football and 90 is largest set of people given, the none could be all remaining, that is 150-90 = 60.
So 60 - 2*all three = 40 or all three = 10.

Note: If someone wants to know all the parts. 
Since everything is a part of F, all parts that do not contain F are 0.
Total = Only h + Only t + Only f + Only h&t + Only h&f + Only t&f+ all three + None  = 150
H = Only h + Only h&t + Only h&f + all three = 0 + 0 + Only h&f + 10 = 40........Only h&f = 30
T = Only t + Only h&t + Only t&f + all three =  0 + 0 + Only t&f + 10 = 50........Only t&f = 40
F = Only f + Only f&t + Only h&f + all three =  Only f + 30 + 40 + 10 = 90........Only f = 10
 ­
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chetan2u
­At Rocket Brown Elementary School there are 150 students and three sports teams – hockey, tennis, and football. Rocket Brown students are allowed to participate in as many of the three sports as they like or to abstain from participation completely. At the beginning of the semester, 40 students choose to play hockey, 50 choose to play tennis and 90 choose to play football, while 70 decide to play exactly two sports simultaneously.

In the table, select a value that would be the greatest number of students who could choose to play all three sports and the greatest number of students who could choose to play no sports at all. Make only two selections, one in each column.­
­Check out this video on Max-Min in Overlapping Sets first:
https://youtu.be/oLKbIyb1ZrI

Now note that "All" and "None" both will be maximized together. When "All" is maximum, "None" is maximum too (keeping other overlaps constant).

Since of 150, 90 people do play football, None can be at most 150 - 90 = 60
Both other circles will lie inside the football circle in this case. For an overlap of 70 for exactly 2 sports, first let's overlap 10 instances of tennis with 10 of football for an overlap of two sports. Now we have 40 instances each of tennis and hockey and we need another 60 overlap of two sports. Hence 30 of tennis and 30 of hockey should overlap with football independently so that we have a 70 overlap for exactly 2 sports. Now we have 10 instances of both tennis and hockey leftover to overlap with football for the All region. This is what the diagram looks like:

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Screenshot 2024-04-24 at 6.34.57 PM.png
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Answer:
10 - Both
60 - None


 ­
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Bunuel
Out of the 150 students at Rocket Brown Elementary School, 90 joined the football team, 50 joined the tennis team, 40 joined the hockey team, and 70 joined exactly two of these teams.

Select for None the maximum number of students who could have chosen not to join any of the three teams, and select for All three the maximum number of students who could have joined all three teams.

150 = (90+50+40) - (70) -2d + a

150 = 110 -2d+a
-2d = 40 -a

take d = 0, doesnt work
take d = 10, -20 = 40 - 60 = -20 = -20, hence max = 10, none = 60
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