Mathematical problems of mixed operation of mathematical fractions 1. Shuanghu primary school has 1300 students. Among them, the lower grade is one fourth less than the middle grade, and the middle grade is one third less than the higher grade. How many students are there in the lower, middle and higher grades? 2. A, B and C save one third of the money of the other two, and have saved one fourth of the money of the other two. C saves 660 yuan? 3. Two fifths of Lao Wang's weight is equal to two-thirds of Lao Li's. three fifths of Lao Wang's weight is 1.5kg lighter than seven fourths of Lao Li's. how many kilos do Lao Wang and Lao Li weigh?

Mathematical problems of mixed operation of mathematical fractions 1. Shuanghu primary school has 1300 students. Among them, the lower grade is one fourth less than the middle grade, and the middle grade is one third less than the higher grade. How many students are there in the lower, middle and higher grades? 2. A, B and C save one third of the money of the other two, and have saved one fourth of the money of the other two. C saves 660 yuan? 3. Two fifths of Lao Wang's weight is equal to two-thirds of Lao Li's. three fifths of Lao Wang's weight is 1.5kg lighter than seven fourths of Lao Li's. how many kilos do Lao Wang and Lao Li weigh?

1. Let the senior grade be 1, the middle grade be 1-1 / 3 = 2 / 3, and the junior grade be (1-1 / 4) times 2 / 3 = 1 / 2
There are 1300 senior students divided by (1 + 2 / 3 + 1 / 2) = 600
There are 600 students in the middle grade
There are 1300-600-400 = 300 people in lower grades
2. Party A deposits (1 / 3) / (1 + 1 / 3) = 1 / 4 of the total amount
The amount of money saved by Party B is 25% / (1 + 25%) = 1 / 5
C deposit is 1-1 / 4-1 / 5 of the total amount = 0.55
Because C saved 660 yuan
So the total is 660 / 0.55 = 1200 yuan
The deposit of Party A is 1200 * 1 / 4 = 300 yuan, and the deposit of Party B is 1200 * 1 / 5 = 240 yuan
3. Solution: let Lao Wang's be x and Lao Li's be y
2\5X=2\3 3\7X=3\4Y-1.5
X=70 Y=42