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Relations — Maths STD 11 Science — Question

CBSE BoardEnglish MediumSTD 11 ScienceMathsRelations3 Marks
Question
If A and B are two set having 3 elements in common. If n(A) = 5, n(B) = 4, find n(A × B) and $\text{n}\big[(\text{A}\times\text{B})\cap(\text{B}\times\text{A})\big]$
✓

Answer

We have,
n(A) = 5 and n(B) = 4
We know that, if A and B are two finite sets n(A × B) = n(A) × n(B)
$\therefore$ n(A × B) = 5 × 4 = 20
Now,
$\text{n}\big[(\text{A}\times\text{B})\cap(\text{B}\times\text{A})\big]=3\times3=9$ $\big[\because$ A and B have 3 elements in common$\big]$

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