If you ask old Ursula how many cats she has at home, she answers sadly: "Four-fifths of my cats plus four-fifths of a cat." How many cats does this add up to?
She has 4 cats......
(4/5) of them = (4/5)4 = 16/5 = 3.2 cats
And 4/5 of 1 cat = .8 of a cat
So.....3.2 cats + .8 of another = 4
Algebraically.....let N be the number of cats......
Then.....
(4/5)N + 4/5 = N
4/5 = (1/5)N
And it's obvious that N = 4......