Addition and subtraction calculation of fractions

1, knowing arithmetic, can calculate the addition and subtraction method of fractions with the same denominator within 20.

2, can correctly calculate the addition and subtraction of fractions with the same denominator within 20.

3. By observing the music score wall, you will find the related knowledge of music score and learn it initially? Observe, discover, transform? Equal mathematical thinking method.

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1, knowing that any point on the ray can be represented by a number. Realize? Scores? Where does the concept come from? Process? Arrive? Object? Change.

2. The scores will be compared on several rays. And can directly compare the sizes of the same denominator or the same molecular fraction.

3. Master the addition and subtraction calculation of fractions with the same denominator.

Fraction size comparison

1, will compare the same denominator fraction or the same numerator fraction.

2. Solve related simple practical problems.

3. Recognize that different scores can represent the same quantity.

4. Know the same score; You will find that the scores are equal.

Understanding of Numbers within 1 100 million

Example 1: Let students understand that the quota of 1 1 10,000 is110,000; 100000 is one million; 101 million is 10 million; 10 10 million is 100 million. One, ten, hundred, thousand and ten thousand are all units of counting. There is a decimal relationship between every two adjacent counting units. In our country's counting habit, every four digits are level 1, level 2, level 10,000 and level 100 million.

Example 2: Multi-digit reading method: When reading, read first grade, then read 100 million grades from high to low, then read 10,000 grades, and finally read first grade. No matter how many there are at the end of each grade, don't read them.

Example 3: How to write multi-digits: write 10,000 levels first, and then write one level. If any number has no previous unit, write 0 as a placeholder.

Example 4: Comparison of numbers within 100 million: the number of digits is different, and the number with more digits is larger; Same number of digits; The largest number from the left is the largest; If the numbers in the first position from the left are the same, compare the numbers in the second position from the left until the size is compared.

Example 5: in order to facilitate reading and writing, rewrite the whole 110 million place number into use? Billion? 、? Wan? Do the number of units.

Example 6: Rounding method: To find the approximate value of a number, it mainly depends on whether the number of the highest digits omitted by it is less than, greater than or equal to. If the highest digit of the omitted mantissa is less than or equal to, all mantissas are discarded. If the number on the highest digit of the omitted mantissa is greater than or equal to, the mantissa is omitted and one digit is advanced.

1. About approximate figures:

(1) In practical problems, some data are exact figures that are completely in line with reality. Class 3 boys 12, girls 27. Here? 1227? It's all accurate.

(2) There are still some data, which are only approximate figures that are generally in line with the actual situation. When we measure the length and mass of an object, due to the limitation of measuring tools, errors will inevitably occur, and the results obtained are approximate. Xiao Ming is 140 cm tall and weighs 35 kg. Here? 140? 、? 35? It's all approximate figures.

(3) When a large number is counted, it is generally only needed to be represented by its divisor. People usually say that a city is crowded with people, and a steel plant produced 1 10,000 tons of steel last year. Here? Wan? 、? Wan? It's all approximate figures.

1, vertically parallel: ① Two straight lines that do not intersect the same plane are called parallel lines, which can also be said to be parallel to each other. (2) If two straight lines intersect at right angles, they are said to be perpendicular to each other, one of which is called the perpendicular of the other, and the intersection of these two straight lines is called the vertical foot.

2. Draw a vertical line: ① How to draw a vertical line through a point on a straight line? Just draw a straight line along the other right angle with a pen. (2) The method of drawing the vertical line of a straight line through a point outside the straight line? Just draw a straight line along a right angle side of the triangular ruler, and the other side of the triangular ruler is close to the point outside the straight line. ③ Connect a point outside the straight line with any point on the straight line, which line segment is the shortest? The vertical line segment drawn from a point outside the straight line is the shortest, and its length is called the distance from that point to the straight line.

3. Draw parallel lines: ① How to draw parallel lines? Draw parallel lines with a ruler and a triangular ruler. First, put one right angle side of the triangular ruler close to a straight line, and then put the ruler close to the other right angle side of the triangular ruler. At this point, translate the triangular ruler along the ruler and draw a straight line. ② Draw several lines perpendicular to the parallel lines between two parallel lines. What are the length characteristics of these lines? The distance between two parallel lines is equal. ③ How to draw a rectangle? The opposite sides of a rectangle are parallel to each other, and the two sides are perpendicular to each other. Therefore, you can draw vertical lines or parallel lines.

4. Parallelogram: Two groups of parallelograms with parallel opposite sides are called parallelograms; A quadrilateral with only one set of parallel sides is called a trapezoid. When the two waists of a trapezoid are equal, the trapezoid with equal waists is called an isosceles trapezoid. A quadrilateral with four corners at right angles is called a rectangle. A quadrilateral with four right angles and four equal sides is called a square.

5. Trapezoid: parallelogram is easy to deform and has no stability.