Assuming the salt concentration in lake parsons before it became isolated was equal to the average salt concentration in nearby non-isolated lakes, calculate the percentage of lake parsons which has evaporated since it became isolated.

Assuming the data for the problem is:

- salt concentration of Lake Parsons: 21 g/L
- salt concentration of other Lakes: 6.67 g/L

This means that the salinity on Lake Parsons is now 3.15 times (21/6.67=3.15) bigger, which means that the amount of water in the lake has been reduced 3.15 times. So in order to know the percentage of water the Lake has now, we must divide 100% between 3.15 (100/3.15= 31.75%), and to know the percentage lost we substract that amount from 100% (100-31.75=68.75%), giving us the final result.

Are you asking about a street map usage  if so here is your answer  a street map for a very limited area could simply be a bit map or a .jpg image.  but a more general map would probably store the streets as vectors.  but you shouldn't assume that there is one way to do it