Counting…

There are 80 houses in a neighborhood. There are a total of 18 dogs in the neighborhood, 30 houses do not have any pets. 20 houses have both cats and dogs. How many cats are there in this neighborhood ?

what do you need to learn ?

you should know , how to count and if you happen to count some of them twice, you need to subtract them.

p(AUB) = p(A) + p(B) — p (AnB).

There are 10 entities in here . cat, dog, house, me, nila , moon, skater, dancer, singer, coder.

Total number of houses = 80

Total number of dogs in this hood = 18

Total number of cats in this hood = ?

Houses that has both cats and dogs = 20

houses do not have any pets = 30

houses that have pets = 80–30 = 50

50 = ? + 18 — 20

Total number of cats = 52

me : Is my answer right ?

Nila : Nope , my answer is 48 cats.

me : Wait what ? Okay let me rewrite the problem again.

There are 80 houses in a neighborhood. There are a total of 20 dogs in the neighborhood, 30 houses do not have any pets. 18 houses have both cats and dogs. How many cats are there in this neighborhood ?

50 = ? + 20 — 18

Total number of cats in the neighborhood = 48.

Nila : Do you want to talk about expectations , long-run averages, data structures, design patterns or coconut husks ?

Me : May be another day.