Answer:
7 dm
Step-by-step explanation:
One side is 1 dm while the other is 3 dm, so first you should add 1 and 3 together, and you get 4. you know that the answer has to be an integer. if this is an isosceles triangle then the last side has to be either 1 or 3. the last step is to add all three sides together.
-Char-