Raising animals together

Baidu O & M Department

Reasoning: 24 people each have at least one type of PET, with 13, 5, 10, and 9 birds, dogs, fish, and cats respectively, at the same time, there are 4 birds and fish, birds and cats, and fish and cats. How many people are there with only one type of pets? How many people are raising birds, fish, and cats?

Thought 1:

Bird, dog, fish, cat 13 5 10 9 | -- 2 -- | ----- 4 ---- | -- 4 -- | -------- 4 ------- | only bird: X dog: y fish: Z only cats: m birds, fish, and cats: F birds: x + 2 + 4 + 4-F = 13 ;=> x = 3 + F dogs: Y + 2 = 5; => Y = 3 for fish farming: Z + 4 + 4-F = 10; => Z = 2 + F for cats: m + 4 + 4-F = 9; => M = 1 + F minus 2f when calculating the number of people who raise Birds, birds, and cats together, three times, I repeated two times. The number of students raised together is 24 = x + y + Z + m + 2 + 4 + 4 + 4-2f => 7 = x + Z + M. -2f 7 = 6 + 3f-2f => F = 1 => X = 4 Y = 3 Z = 3 M = 1

Thought 2:

Birds, dogs, fish, and cats are 13, 5, 10, and 9 people respectively. That is to say, there are 13 + 5 + 10 + 9 = 37 pets in total, there are X persons in three types of maintenance, and y persons in two types of maintenance (24-x-y) + 2y + 3x = 37, then we can count the people who do not raise dogs to raise two animals: y-2 people who only raise birds and fish, birds and cats, fish and cats 3 (4-x ), that is, the y-2 = 3 (4-x), constitute a two-element equations, can be solved.