See the attached picture.
Triangles ABC and A'B'C are similar. This means that the corresponding sides are in the same ratio, in this case:

Replacing with data:
Answer:
Because 180 is bigger than 3 and your trying to divide 180 into 3. Which isn't gonna come out an even number. 0.01666666666 is a lot smaller than 3.
Step-by-step explanation:
Hope this helped!!!