Question

If $A=(5,6,7,8,9),B=\{x:3<x<8\text{and}x\in W\}$ and $C=\{x:x\le 5\text{and}x\in N\}$. Find number of elements in B $\cup$ C.

Answer 1

Given,$A=(5,6,7,8,9),B=\{x:3<x<8\text{and}x\in W\}$ and $C=\{x:x\le 5\text{and}x\in N\}$.

From the given sets, we have

$B$ $=$ { $4,5,6,7$ } as $x$ is greater than $3$ but less than $8$
And $C$ $=$ { $1,2,3,4,5$ } as $x$ is a natural number less than equal to $5$.

Union of two sets has all the elements of both the sets
So, $B\cup C=$ { $1,2,3,4,5,6,7$ }

$n(B\cup C)=7$