Question

If the average of $3$ and $x$ is $5$ and the average of $5$ and $y$ is $7$, what is the average of $x$ and $y$?

• A. 6
• B. 7
• C. 8
• D. 9

Answer 1

Answer: (C)

8

Average of $3$ and $x$ is $5$

$\therefore \frac{3+x}{2}=5$

$\Rightarrow 3+x=10$

$\Rightarrow x=10-3$

$\Rightarrow x=7$

Average of $5$ and $y$ is $7$

$\therefore \frac{5+y}{2}=7$

$\Rightarrow 5+y=14$

$\Rightarrow y=14-5=9$

Then average of $x$ and $y=$ $\frac{7+9}{2}=\frac{16}{2}=8$