Final answer:
To convert millimeters to decimeters, divide the length in millimeters by 10. So, a 3.5 mm long insect is equal to 0.35 decimeters.
Step-by-step explanation:
To convert millimeters (mm) to decimeters (dm), we need to divide the length in millimeters by 10. So, to find how many decimeters a 3.5 mm long insect is, we divide 3.5 mm by 10.
3.5 mm ÷ 10 = 0.35 dm
Therefore, a 3.5 mm long insect is equal to 0.35 decimeters.