A2. Seven consecutive odd numbers add up to 105 . What is the largest of these numbers?
SolUTION
21

Let the fourth odd number be $x$. Then $(x-6)+(x-4)+(x-2)+(x)+(x+2)+(x+4)+(x+6)=105$. This simplifies to $7 x=105$, which gives $x=15$. The largest of the seven consecutive odd numbers is $15+6=21$.