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How to do the math problems of chickens and rabbits in the same cage in the second volume of the fourth grade
The solution of math problems of chickens and rabbits in the same cage in grade four;

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