How many guppies?

From Marilyn Vos Savant’s column in Parade Magazine, June 19, 2016

Say you have 200 fish in an aquarium, and 99 percent of them are guppies. You want to reduce the proportion of guppies to exactly 98 percent. How many should you remove?
— M.S., Winston-Salem, North Carolina

Give it a try.  The answer is surprising.

In this tank of fish, 198 are guppies. If you remove two, they will still constitute almost 99 percent of the fish (196 guppies in a tank of 198 fish equals 98.9898… percent). Even removing 20 guppies won’t help much more. Their proportion will still be 98.8888… percent. You would need to remove 100 guppies to drop their proportion to 98 percent (98 guppies in a tank of 100 fish).