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Byju's Answer
Standard XII
Mathematics
Union
A set A has...
Question
A set
A
has
3
elements and another set
B
has
6
elements. Then
A
3
≤
n
(
A
∪
B
)
≤
6
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B
3
≤
n
(
A
∪
B
)
≤
9
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C
6
≤
n
(
A
∪
B
)
≤
9
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D
0
≤
n
(
A
∪
B
)
≤
9
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Solution
The correct option is
C
6
≤
n
(
A
∪
B
)
≤
9
n
(
A
)
=
m
1
n(B)=
m
2
we know that
n(A
∪
B)=n(A)+n(B)-n(A
∩
B)
∴
the greatest value of n(A
∪
B) is when
n
(
A
∩
B
)
=
0
∴
n(A
∪
B)=
m
1
+
m
2
∴
least value of
n
(
A
∪
B
)
= min(A,B)
∴
least value of
n(A
∪
B) =
m
2
....when
n
(
A
∩
B
)
= m
1
=
m
1
....when n
n
(
A
∩
B
)
=
m
2
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Similar questions
Q.
Assertion :If
n
(
A
)
=
3
,
n
(
B
)
=
6
, then maximum number of elements of
n
(
A
∪
B
)
=
9
Reason:
n
(
A
∪
B
)
will be maximum if
n
(
A
∩
B
)
is minimum.
Q.
If A and B are two sets having 3 elements in common. If n(A)=6 and n(B)=4, then
n
(
(
A
×
B
)
∩
(
B
×
A
)
]
=