In order to get 25% of somthing first you need to find 50%.
This is easy because all you have to do is half it.
In this case 50% would be 3.2 becuase 6.4 divided by 2 is 3.2
You now need to half the 50% which will give you 25%
3.2 divided by 2 = 1.6
25% of 6.4cm = 1.6cm
