1. Recall the 5 bridge problem you studied in this lesson. As you saw, any path
which uses each bridge once and only once had to start at the points B or D since
there were three lines connected to them.
A. List all possible paths which use each bridge once and only once.
B. Can you add one bridge so that there is no possible path which uses each bridge only once? If so, give one example.
C. Can you add one bridge so that it is still possible to find a path which uses each bridge only once? If so, give one example.

1. 180°. the sum of the interior angles of a triangle is 180°, for the equilateral triangle that it has three equals side is 60°+60°+60°=180°.

2. 60°. each interior angle of a equilateral triangle is 60°

3. 120°. the measure of ∠m is 120°, the sum of the angles ∠m and ∠n is equal to 180°. so, in order to find the measure of ∠m, we have ∠m+∠n=180° > ∠m=180°-∠n > ∠m=180°-60°=120°.

4. 360°. the sum of the exterior angles of an equilateral triangle is ∠m+∠r+∠x=120°+120°+120°=360°. the exterior angles of any triangle always add 360°.