Beijing Normal University seventh grade first volume mathematics

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"Mixed Operations of Addition and Subtraction of Rational Numbers" Rational numbers and their operations PPT courseware

Add a "+" or "-" sign in front of the numbers 2, 3, 4, 5, 6, 7, 8, and 9 so that their sum is 10. How many ways can you find?

2 3 4 5 6 7 8 9

Example 1 Fill in the blanks:

(-8)+____=-5; (-8)+____=-3;

8+ =-7; (-8)+ =4

(-8)-____=-5; (-8)-____=-3;

8-____ =-7; (-8)-____=4

Solution: (-8) + 3 = -5; (-8) + 5 = -3;

8+ (-15)=-7; (-8)+ 12 =4

(-8)-(-3)=-5; (-8)-(-5)=-3;

8-15=-7; (-8)-(-12)=4

Homework

1. One day, Xiao Ming was running on a north-south road. He started from point A and recorded his running situation every 10 minutes (south is the positive direction, unit: meters): -1008, 1100, -976, 1010, -827, 946. One hour later he stopped to rest. In what direction was he at A at this time? How far is it from point A? How many meters did Xiao Ming run in total?

2. For 10 boxes of apples, if each box is based on 20 kilograms, the excess kilograms will be recorded as a positive number, and the insufficient kilograms will be recorded as a negative number. The weighing records are as follows: +2, +1, 0, -1, -1.5, -2, +1, -1, -1, -0.5.

What is the total weight of these 10 boxes of apples in kilograms?

3． There are 4,000 kilograms of grain originally stored in the warehouse. The deposit and withdrawal conditions within a week are as follows (deposit is positive, unit: kilogram): 2000, -1500, -300, 600, 500, -1600, -200.

Ask how many kilograms of grain are still in the warehouse at the end of the 7th day?

4. There is 3,500 yuan in my mother's passbook. I took out 1,600 yuan to buy a washing machine and deposited another 700 yuan. How much money is left in the passbook?

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For more information about the PPT courseware "Addition and Subtraction Mixed Operations of Rational Numbers, Rational Numbers and Their Operations", please click the Addition and Subtraction Mixed Operations of Rational Numbers ppt Rational Numbers and Their Operations ppt tag.

"Mixed Operations of Addition and Subtraction of Rational Numbers" PPT courseware:

"Mixed Operations of Addition and Subtraction of Rational Numbers" PPT courseware review review (1) What is the addition rule of rational numbers? The addition rules of rational numbers: (1) When adding two numbers with the same sign, take the same sign and add the absolute values; (2) When adding two numbers with different signs with unequal absolute values, take the absolute value comparison..

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Update Time: 2024-10-02

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