Question

If $Y\cup \{1,2\}=\{1,2,3,5,9\}$, then

• A. The smallest set of $Y$ is $\{3,5,9\}$
• B. The smallest set of $Y$ is $\{2,3,5,9\}$
• C. The largest set of $Y$ is $\{1,2,3,5,9\}$
• D. The largest set of $Y$ is $\{2,3,4,9\}$

Answer 1

Answer: (A), (C)

The correct options are
A The smallest set of $Y$ is $\{3,5,9\}$
C The largest set of $Y$ is $\{1,2,3,5,9\}$

Since the set of the right hand side has $5$ elements,

$\therefore$ smallest set of $Y$ has three elements and largest set of $Y$ has five elements,

$\therefore$ smallest set of $Y$ is $\{3,5,9\}$

and largest set of $Y$ is $\{1,2,3,4,9\}$