1, hypothesis method:

Suppose all rabbits, (the number of feet per rabbit x the number of heads-the original total number of feet) ÷ (the number of feet per rabbit-the number of feet per chicken) = the number of chickens; Number of heads-number of chickens = number of rabbits

Assuming all chickens, (original total number of feet-number of feet per chicken x number of heads) ÷ (number of feet per rabbit-number of feet per chicken) = number of rabbits; Number of rabbits = number of chickens

For example, chickens and rabbits live in the same cage, with 20 heads and 50 feet. How many chickens and rabbits are there respectively?

(4x20-50)÷(4-2)= 15 (only) ... Chicken; 20- 15 = 5 (only) ... Rabbit

(50-2x20)÷(4-2)=5 (only) ... Rabbit; 20-5 = 15 (only) ... Chicken

2, lift foot method:

When the chicken and rabbit lift their feet at the same time, the total number of feet in the cage is reduced by 2. A chicken has only two feet, and there are only two rabbits in the cage. Number of remaining feet ÷ 2 = number of rabbits.

(total number of feet-total number of heads × number of chicken feet) ÷ (number of feet per rabbit-number of feet per chicken) = number of rabbits.

Total number of rabbits = number of chickens

For example, chickens and rabbits live in the same cage, with 20 heads and 50 feet. How many chickens and rabbits are there respectively?

(50-20× 2) ÷ 2 = 5 (only) ...

20-5 = 15 (only) ... Chicken