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Question: Answered & Verified by Expert
A and $\mathrm{B}$ are two sets having 3 elements in common $\operatorname{lfn}(\mathrm{A})=5, \mathrm{n}(\mathrm{B})=4$, then what is $\mathrm{n}(\mathrm{A} \times \mathrm{B})$ equal to
MathematicsSets and RelationsNDANDA 2014 (Phase 2)
Options:
  • A 0
  • B 9
  • C 15
  • D 20
Solution:
1065 Upvotes Verified Answer
The correct answer is: 20
Here, $\mathrm{n}(\mathrm{A})=5$ and $\mathrm{n}(\mathrm{B})=$
$\cdot n(A \times B)=5 \times 4=20$
$[\because \mathrm{n}(\mathrm{A})=\mathrm{m}, \mathrm{n}(\mathrm{B})=\mathrm{n} \Rightarrow \mathrm{n}(\mathrm{A} \times \mathrm{B})=\mathrm{mn}]$

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