Know the total number of head and feet, and then ask the formula of chicken and rabbit:

Number of rabbits = (total number of feet-number of chicken feet × number of rabbits) ÷ (number of rabbit feet-number of chicken feet)

Number of chickens = (rabbit's feet × total feet-total feet) ÷ (rabbit's feet-chicken's feet)

Method 1: Suppose they are all chickens.

The total number of feet will be 2, and the actual number of extra feet = the actual number of feet-the total number of feet 2. The actual number of extra feet is because there are rabbits, and each rabbit has two extra feet. The number of rabbits = the actual number of extra feet.

Number of rabbits = half of the actual total number of feet-total number of heads

Method 2: Assuming they are all rabbits,

The total number of feet will be equal to 4 total heads, and the actual number of feet is less than that of rabbits. Because there are chickens, each chicken has two feet less than the rabbit.

The actual number of feet is less than that of rabbits. A few missing two is the number of chickens.

Number of chickens =2 total heads-half of the actual total number of feet

Leg lifting method

Method one

If the chicken raises one foot and the rabbit raises two feet, there are half (only) feet in the total number of feet. There are more rabbits in the cage than chickens 1 foot. At this time, the difference between the total number of feet and the number of heads = half of the total number of feet-the total number of feet = is the number of rabbits.

Method 2

If both the chicken and the rabbit lift their feet, that is, the chicken has no feet floating in the air, and the rabbit has only two feet, leaving (the total number of feet-two heads) feet. At this time, there are only rabbit feet on the ground, and each rabbit has two feet on the ground, so the number of rabbits = half (total number of feet-two heads) = actual total number of feet-half of the total number of heads.

Method 3

We can let the rabbit lift two feet first, so there are two feet in total, the difference between the number of feet and the original total number of feet-two feet in total. These are all about each rabbit lifting two feet and one * * * lifting (total number of feet-two total numbers of heads), and the number of rabbits = (total number of feet-two total numbers of heads) = half of the actual total number of feet-

Method 4

Let all rabbits lift their front legs, and only two hind legs land like chickens. In fact, if there are only two feet like a chicken, there will be two feet in total. Less feet = total feet-two total heads = two rabbits.

Number of rabbits = half of the actual total number of feet-total number of heads

Method 5

Hypothetical method (popular)

Suppose both the chicken and the rabbit lift one foot, the chicken becomes a golden rooster, and the rabbit becomes a three-legged rabbit. The foot standing in the cage = the actual total number of feet-the total number of heads (only)

Then lift one foot. At this time, the chicken falls when its feet are raised. It sat on the ground with its butt, leaving only two rabbits standing on its feet. The number of feet left = actual total number of feet -2 total head (only), and the number of rabbits = half (total number of feet -2 total head) = half of actual total number of feet-total head.

Chicken lower wing method

Let all chickens put their wings down as feet, which are actually four feet like rabbits, and there will be four feet in total. Extra feet = four heads in total-two feet in total = two chickens.

Number of chickens =2 total heads-half of the actual total number of feet

After the third grade

Formula: the number of chickens = 2 times of the total number of heads-half of the total number of feet, and the number of rabbits = half of the total number of feet-the total number of heads.

Number of chicken feet = 2 times the number of chickens

Number of rabbits = total number of heads-number of chickens

Number of rabbit feet =4 times the number of rabbits =4 times (total number of heads-number of chickens) =4 times the total number of heads-number of chickens.

Total number of feet = number of chickens+number of rabbits =2 times number of chickens +(4 times number of chickens -4 times number of chickens) =4 times number of chickens -2 times number of chickens

2 times the number of chickens = 4 times the total number of heads-the total number of feet.

Number of chickens = 2 times of the total number of heads-half of the total number of feet

Number of rabbits = total number of chickens = total number of rabbits-(twice the total number of rabbits-half the number of feet) = half the number of feet-total number of chickens.

Equation method

Number of chickens = 2 times of the total number of heads-half of the total number of feet

Number of rabbits = half of the total number of feet-total number of heads

Method one

Suppose the number of rabbits in it is X.

Then the number of chickens is the total number-X.

Total Feet =4x+2 (Total Feet -x)

Total number of feet =2x+2 total number of heads

2x= total number of feet -2 total number of heads

X= (total number of feet -2 total number of heads) /2

X= total number of feet /2- total number of heads

Method 2

Suppose the number of chickens in it is X.

Then the number of rabbits is the total number-x.

Total Feet =2x+4 (Total Feet -x)

2x = total number of 4 heads-total number of feet

X=2 Total number of heads-Total number of feet /2