Unit 65438 of the first volume of the fourth grade mathematics examination paper +0-3.

First, estimate. (use a number close to the integer million or the integer billion? Rounding? When you find the approximate number, add or subtract it. )

For example:

2039800+40 15 13? 2.04 million+400 thousand = 2.44 million

365249030-30059 1730? 400-300 million = 1 100 million

85039400+2530980? Wan+Wan = Wan

845249030-370059 173? Billion-Billion = Billion

If you are familiar with it, you can omit the intermediate process, but remember to write the counting unit and? .

859507+2 10759? 5768005700+207400853?

584204-237599? 92 10055732-395008427?

57 1507+4 17059? 75200483 17+3 15700455?

7 14204-237599? 7580045 120-4 10750324?

524760+2 10759? 1275005700+420076250?

752824-472088? 8004560003-527 144400?

Second, oral calculation. (rewrite the integer of 10 thousand or 100 million to use? Wan? Or? Billion? After working in the unit, it is much easier to do oral calculations. )

For example: 260000+170000 = 260000+17000 = 430000.

450000000000-500000000 = 4.5 billion-500 million = 4 billion.

840000+ 160000= ten thousand-ten thousand = ten thousand

32000000000-180000000 = billion-billion = billion

If you are familiar with it, you can omit the intermediate rewriting process, but remember to write the counting unit.

850000+430000= 7300000000+500000000=

580000-240000= 8200000000-300000000=

460000+230000= 3700000000+ 100000000=

4 10000- 190000= 8300000000-600000000=

770000+230000= 2400070000+ 140590000=

4 10000- 190000= 7845600000-350500000=

Third, use the relationship between the parts of addition and subtraction to solve the problem.

One addend = and-the other addend.

Minus = Difference+Minus = Minus-Difference

1, and fill in the appropriate numbers in brackets.

( )-560=700 ( )+800= 1900

( )-500=800 ( )+ 150=8500

( )-325=525 ( )+780= 1000

( )-420=520 ( )+950=3500

980-( )=650 450+( )=2800

800-( )=450 580+( )= 1500

750-( )=430 790+( )=2000

940-( )=520 350+( )=2400

2. Calculate the following questions and check them.

360+ 180 820-450 790+460

864-379 527+695 803-587

785+678 500-32 1 784+576

5048-4909 7903+ 157 3850-908

3. Solve practical problems.

(1) Wang San got 185 in Chinese mathematics last time, and 97 in mathematics. What's the score of Chinese?

(2) Dad brought 300 yuan money, spent 125 yuan to buy clothes, bought a schoolbag and returned it 160 yuan. How much is this bag?

(3) Mom took some money to go shopping, bought shoes with 80 yuan, spent 150 yuan on clothes, and left 170 yuan. How much money did mom bring to the street?

(4) A story book, I read 8 pages on the first day and 9 pages on the second day, 13 pages. How many pages does this story book have?

Four, several knowledge points calculated by simple methods.

1, additive commutative law: When several numbers are added, the positions of addends are exchanged, and their sums remain unchanged. Expressed in letters: A+B+C = B+C+A = C+A+B.

2. Law of addition and combination: When several numbers are added, the first two numbers are added and then the third number is added, or the last two numbers are added and then the first number is added, or the first number and the third number are added and then the second number is added. Their sum remains the same.

Expressed in letters: A+B+C = (A+B)+C = A+(B+C) = (A+C)+B.

3. The operational nature of subtraction: If a number subtracts several numbers in succession, it is equal to the sum of these subtractions in the minuend.

Expressed in letters: a-b-c=a-(b+c)

4. Add or subtract a number close to the whole hundred from a number.

(1) Add a few more and subtract a few. For example: 785+ 198

=785+200-2

=985-2

=983

(2) add a few less and add a few more. For example: 356+205

=356+200+5

=556+5

=56 1

(3) reduce a few. For example: 957-304

=957-300-4