Solution
= Solution
The terms form an <arithmetic progression> with <common difference> $2$. There are $(55-5)/2+1=26$ terms. The <arithmetic series> formula gives
$$
\boxed{\frac{26(5+55)}2=780.}
$$
= Solution
The terms form an <arithmetic progression> with <common difference> $2$. There are $(55-5)/2+1=26$ terms. The <arithmetic series> formula gives
$$
\boxed{\frac{26(5+55)}2=780.}
$$