250/100=80000/?
What number do we need to multiply 250 by to get 80000? 80000/250=8000/25=320.
We need to use the same multiplier for 100:
250/100=320*250/(320*100)=80000/32000.
I prefer to do it this way:
80000/250%=80000*100/250=8000*100/25=8000*4=32000.