640 decimeters in kilometers

Conversion formula
How to convert 640 decimeters to kilometers?

We know (by definition) that: $1\mathrm{dm}=0.0001\mathrm{km}$

We can set up a proportion to solve for the number of kilometers.

Now, we cross multiply to solve for our unknown $x$:

Conclusion: 640 ⁢ dm = 0.064 ⁢ km

Conversion in the opposite direction

The inverse of the conversion factor is that 1 kilometer is equal to 15.625 times 640 decimeters.

It can also be expressed as: 640 decimeters is equal to $\frac{1}{\mathrm{15.625}}$ kilometers.

Approximation

An approximate numerical result would be: six hundred and forty decimeters is about zero point zero six kilometers, or alternatively, a kilometer is about fifteen point six one times six hundred and forty decimeters.