1. Divide each side of $\triangle A B C$ into $n$ equal parts, and draw lines parallel to the other two sides through each division point. How many parallelograms are there in total with these lines as sides?
( Hint: For each parallelogram whose sides are not parallel to $BC$, extend the two pairs of opposite sides to intersect $BC$ at three or four points. Then use the result from Example 1. The answer is: $3 C_{n+2}^{4}$ )