Do you really want to solve this practical problem?

The first step is to calculate the volume of copper coil. The specific gravity of copper is 8.9 g /cm?

640000 g /cm？ =640000 g× cm? /8.9g = 7 19 10. 1 1 . cm？

Step 2, calculate the cross-sectional area of the copper coil (assuming there is no hollow inner diameter)

7 19 10cm？ ÷0.2 1cm=342428.57cm？

The third step is to calculate its length.

342428.57cm？ 0.07cm = 4891836.7cm = 48918.367m.

Answer: The length of copper strip is about 48918m.

If the unit is not mistaken, that's it.

Good luck, goodbye.