"Numbers represented by letters" Integers and their addition and subtraction PPT download

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"Numbers represented by letters" Integers and their addition and subtraction PPT download

Part One Content: Basic Knowledge Key Points

Knowledge point 1: Use letters to represent practical problems

1. If you buy 10 items with a unit price of a yuan and pay b yuan (b>10a), then you should get it back (D)

A. ( b-a ) yuan B. ( b-10 ) yuan

C.(10a-b) yuan D.(b-10a) yuan

2. In March 2018, a certain government agency’s three public expenditures were a million yuan. In response to the “eight regulations” and “six bans” advocated by the central government, it began to reduce its three public expenditures. In April, it was 10% less than in March. In May, it was reduced by 10%. If it is 15% less than in April, then the three public expenditures in May are (C)

A.( a-10% )( a-15% ) million yuan

B.(1-90%)(1+85%)a Ten thousand yuan

C.(1-10%)(1-15%)a Ten thousand yuan

D.(1-10%+15%)a ten thousand yuan

Knowledge point 2: Use letters to represent mathematical problems such as operational laws and formulas

4. Use letters to express the commutative law of addition. The wrong one is (C)

A.a+b=b+a B.m+n=n+m

C.p·q=q·p D.x+y=y+x

5. Use letters to indicate the area of ​​the shaded part in the figure below.

Letters representing numbers PPT, part 2: improvement of comprehensive abilities

6. The following patterns are made of matches of the same length according to certain rules. Pattern ① requires 8 matches, pattern ② requires 15 matches... According to this rule, pattern n requires matches (D)

A.(2+7n) root B.(8+7n) root

C.(4+7n) root D.(7n+1) root

7. Observe the equations: ①0×2+1=1, ②1×3+1=4, ③2×4+1=9, ④3×5+1=16,…, then the nth formula is (n- 1)(n+1)+1=n2　.

8. There are boys a and girls B working as volunteers in the community. They move bricks to build a flower bed. The boys each moved 40 yuan, and the girls each moved 30 yuan. Then the boy a and the girl b moved a total of (40a+30b) A brick.

9. Assume n represents an integer. How to express the following characteristic numbers using formulas containing n?

(1) Even numbers and odd numbers;

(2) Three consecutive integers;

(3) Three consecutive odd numbers;

(4) A number that is divisible by 3 with a remainder of 1.

Letters represent numbers PPT, the third part: exploration of expansion and breakthrough

10. Use chess pieces to form the following set of figures:

(1) Use 4 chess pieces to place the first figure, 8 chess pieces to place the 2nd figure, and 12 chess pieces to place the 3rd figure.

(2) If we place it in this way, how many chess pieces will be used to place the nth figure?

(3) Calculate how many chess pieces are used to place the 2019th figure?

Solution: (2) Use 4n chess pieces to place the nth figure.

(3) When n=2019, 4n=4×2019=8076 (pieces).

That is, 8076 chess pieces are needed to place the 2019th figure.

Keywords: Beijing Normal University edition seventh-grade mathematics PPT courseware free download, letter representation of numbers PPT download, integers and their addition and subtraction PPT download, .PPT format;

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Update Time: 2024-10-21

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