# The average of A and B is 10...

• Jan 25th 2007, 12:05 PM
ceasar_19134
The average of A and B is 10...
The average (arithmetic mean) of A and B is 10, whereas the average of B and 10 is C/2. What is the average of A and C?
• Jan 25th 2007, 12:08 PM
ThePerfectHacker
Quote:

Originally Posted by ceasar_19134
The average (arithmetic mean) of A and B is 10, whereas the average of B and 10 is C/2. What is the average of A and C?

This looks like a SAT question.

$\frac{A+B}{2}=10$
$\frac{B+10}{2}=\frac{C}{2}$

Thus,
$A+B=20$ (1)
$B+10=C$ (2)
From (1) subtract (2),
$A-10=20-C$
$A+C=30$
$\frac{A+C}{2}=15$