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Math problems in grades one to five
1. There is a bag of rice and a bag of flour. The weight of rice is 3.6 times that of flour. Flour is 65 kilograms lighter than rice. How many kilograms does rice weigh?

Let rice weigh x kilograms and flour weigh x/3.6.

x-x/3.6=65

3.6x-x=65×3.6

2.6x=65×3.6

x = 90°

Rice weighs 90 kilograms.

2. The area of a rectangle is equal to the area of a square with a side length of 1.2 cm. If the rectangle is 1.6 cm, what is its width?

Suppose it is x centimeters wide.

1.6x= 1.2× 1.2

x=0.9

Its width is 0.9 cm.

Give some oranges to some children. If everyone gets five, there will be six more. If everyone gets six, it's over. How many children are there? * * * How many oranges are there?

Suppose the child has x position.

5x+6=6x

x=6

There are six children.

* * * There are 6× 6 oranges = 36.

4. A canteen has 1600 Jin of rice and several Jin of flour. Now it uses 640 kilograms of rice, and the weight of the remaining rice is exactly twice that of flour. How many kilograms of raw flour?

Suppose the original flour is x kilograms.

2x= 1600-640

x=800-320

x=480

480 kg of raw flour

Two ships, A and B, set off from Shanghai for Qingdao at the same time, with a speed of 36.5 kilometers per hour and a speed of 43.2 kilometers per hour. At this speed, how many hours will Party A fall behind Party B 120.6 km?

Suppose that after X hours, Ship A lags behind Ship B 120.6 km.

43.2x-36.5x= 120.6

(43.2-36.5)x= 120.6

x= 120.6÷6.7

x= 18

18 hours later, ship a lags behind ship b 120.6 kilometers.

6. Both brother and sister leave home for school at the same time. My brother walks 90 meters per minute and my sister walks 70 meters per minute. When my brother arrived at the school gate, he found that he had forgotten his textbook, and immediately went home to get it along the original road. He met his sister at a distance of 120 meters from the school. How many minutes before brother and sister meet? How far is their school?

Suppose brother and sister meet in x minutes.

90x-70x= 120×2

20x=240

x= 12

/kloc-brother and sister meet in 0/2 minutes.

Their school is: 90× 12- 120 = 960m.

7. The distance between the two places is 250 kilometers. A bus and a jeep set off from two places, face to face. The bus starts 50 kilometers first, and then the jeep starts. Buses travel an average of 40 kilometers per hour, and jeeps travel an average of 60 kilometers per hour. A few hours after the jeep set off, the two cars met on the road.

X hours after setting up the jeep, the two cars met on the road.

40x+60x=250-50

100x=200

x=2

Two hours after the jeep left, the two cars met on the road.

8. The distance between Party A and Party B is 132km, and both cars A and B start from two places at the same time and drive in opposite directions. Car A is 48 kilometers per hour, and car B is 36 kilometers per hour. On the way, car B continued to move forward after 1 hour due to fault maintenance. How many hours did the two cars travel from departure to meeting?

Suppose it takes x hours for a car to leave and meet, then it takes x- 1 hour for a car to leave and meet.

48x+36(x- 1)= 132

84x= 132+36

84x= 168

x=2

∴A train took 2 hours from departure to meeting, so B train took 1 hour from departure to meeting.