Operations On Sets

We are given the following information about two disjoint sets $A$ and $B$ :

$n(A)%20%3D%204$ ,

$n(A%20%5Ccup%20B)%20%3D%207$ .

Step 1: Understanding Disjoint Sets

Since $A$ and $B$ are disjoint, they have no common elements. Therefore, the formula for the number of elements in their union simplifies to:

$n(A%20%5Ccup%20B)%20%3D%20n(A)%20%2B%20n(B)$

Step 2: Substituting the Given Values

$7%20%3D%204%20%2B%20n(B)$

Solving for $n(B)$ :

$n(B)%20%3D%207%20-%204%20%3D%203$

Final Answer: $n(B)%20%3D%203$ .

Chapter Questions
1 MCQs