Let the sets of students who passed Mathematics, Physics, and Chemistry be represented by M, P, and C respectively.
From the given data:
Total students, n(U)=50
n(M)=37
n(P)=24
n(C)=43
n(M∩P)≤19
n(M∩C)≤29
n(P∩C)≤20
We need to find the maximum possible value of students who passed all three subjects, which is n(M∩P∩C). Let this value be x.
Step 1: Apply the Principle of Inclusion-Exclusion
The total number of students who passed at least one exam satisfies the inequality:
n(M∪P∪C)≤n(U)
Using the set theory formula for three sets:
n(M∪P∪C)=n(M)+n(P)+n(C)−n(M∩P)−n(M∩C)−n(P∩C)+n(M∩P∩C)
Substituting the known values into the inequality:
37+24+43−n(M∩P)−n(M∩C)−n(P∩C)+x≤50
104−[n(M∩P)+n(M∩C)+n(P∩C)]+x≤50
x≤[n(M∩P)+n(M∩C)+n(P∩C)]−54— (Equation 1)
Step 2: Find upper bounds using individual set constraints
Every student who passes all three exams (x) is inherently part of the groups passing two exams. Therefore, the following conditions must hold true so that the number of students passing only two subjects remains non-negative:
Additionally, the total number of elements belonging to any single set (like Physics) cannot exceed its total given count. Let's look at the constraint for the smallest set, Physics (P=24):
n(P)≥n(M∩P)+n(P∩C)−n(M∩P∩C)
24≥n(M∩P)+n(P∩C)−x
n(M∩P)+n(P∩C)≤24+x— (Equation 2)
Step 3: Maximize the intersection sum
To find the absolute upper limit for x, we substitute Equation 2 and the maximum given limit for n(M∩C)≤29 back into Equation 1:
x≤[n(M∩P)+n(P∩C)]+n(M∩C)−54
x≤(24+x)+29−54
x≤x+53−54
x≤x−1
Since this point defines a boundary on the total universe capacity, let's look at the maximum limits directly. To maximize x, the two-set intersections must be as large as possible. Let's test the maximum values given in the question:
n(M∩P)=19
n(M∩C)=29
n(P∩C)=20
Substitute these maximum values directly into Equation 1:
x≤(19+29+20)−54
x≤68−54
x≤14
Thus, the maximum number of students who could have passed all three examinations is 14.
Correct Answer: A) 14