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Equivalent substitution of Olympic mathematics problems in the fourth grade of primary school [5]
# Elementary School Olympiad # Introduction Tomorrow, this is a beautiful and charming word. May your tomorrow be infinitely beautiful, brilliant and charming! The following is a compilation of "Five Equivalent Substitutions of Olympiad Numbers in Grade Four in Primary School" for your reference.

Tisch

Difficulty:

The weight of a pig is equivalent to the weight of six chickens, and the weight of three chickens is equivalent to the weight of four ducks. How many ducks does a pig weigh?

answer

Because the weight of three chickens equals the weight of four ducks, the weight of six chickens equals the weight of eight ducks, and because the weight of one piglet equals the weight of six chickens, the weight of one piglet equals the weight of eight ducks.

extreme

One day's grazing weight in A Niu is equivalent to that of a rabbit for nine days and six sheep for one day. It is known that A Niu eats18kg of grass a day, while a rabbit and a sheep eat * * * how many kilograms of grass a day?

answer

Because A Niu's weight in one day is equal to that of a rabbit in nine days, that is, the weight of a rabbit eating grass in nine days is 18 kg, that is, a rabbit eating grass in one day 18÷9=2 kg; And because the weight of grazing in Niu Yi is equal to the weight of six sheep grazing in one day, that is, the weight of six sheep grazing in one day is 18kg, that is, one sheep grazing in one day 18 ÷ 6 = 3kg, so a rabbit and a sheep grazing in one day is 2+3 = 5kg.

Tisso

The weight of a pig is equivalent to the weight of six chickens, and the weight of three chickens is equivalent to the weight of four ducks. How many ducks does a pig weigh?

Answer and analysis:

Because the weight of three chickens equals the weight of four ducks, the weight of six chickens equals the weight of eight ducks, and because the weight of one piglet equals the weight of six chickens, the weight of one piglet equals the weight of eight ducks.

Article 4

1. Please judge from the above two scales that the number () should be filled in the left bracket of the green apple below.

2. Excuse me, according to the picture below, a () should be filled in brackets.

?

1, analysis and investigation balance substitution. Balance means equality between the two sides. The first balance shows that two red apples are equal to four green apples. Slightly changed, one red apple is equal to two green apples. The second balance shows that a pear is equal to a red apple and a green apple; The third balance asks about the relationship between pears and green apples, so we should convert red apples into apples. 1 red =2 cyan, 1 pear = 1 red+1 cyan, so 1 pear =2 cyan+1 cyan, that is, 1 pear =3 cyan answer 3.

2. Analysis and research of balanced substitution. Balance means equality on both sides. 1 dog =3 rabbits, 1 rabbit =3 ducks, so 1 dog =3 ducks +3 ducks, which means 1 dog =9 ducks.

Answer 9

chapter five

Xiao Ming has money from 40 yuan, more than 6 yuan from Xiao Qiang. How much money do they have? How much did Xiao Ming give Xiao Qiang? They both have the same amount of money.

answer

Xiaoming's money+Xiaoqiang's money = total.

Xiaoming's money-the average of two people = the money Xiaoming wants to give to Xiao Qiang.

Solution: 40+(40-6)=40+34=74 (yuan)

40-(40+34)-2 = 40-37 = 3 (yuan)

They have 74 yuan. Xiao Ming gave Xiao Qiang as much money as Sanyuan.