"Unit of Length" PPT

Description

"Unit of Length" PPT

Part One: Review Station

1. The need for unified length units

Using different items as measurement units to measure the same item will yield different results.

2. Know centimeters and meters

Centimeters and meters are units for measuring the length of objects. When measuring the length of shorter objects, use "centimeters" as the unit; when measuring the length of longer objects, use "meters" as the unit.

For example: the length of a thumbtack is about 1 cm; if a child stretches out his arms, the length between the two arms is about 1 meter.

Meters are represented by the letter "m" and centimeters are represented by the letter "cm".

3. Relationship between meters and centimeters

1 meter = 100 centimeters. According to the relationship between centimeters and meters, some conversions between length units can be made.

For example: 70 cm + 30 cm = (1) meter 1 meter - 20 cm = (80) cm

Note: When calculating, it depends on whether the length units are uniform. If not, the units must be unified first and then calculated.

4． Use a scale to measure the length of an object

Align the scale 0 of the ruler with one end of the object, and then see how much the other end of the object faces the scale.

5. Recognize line segments

(1) Characteristics of a line segment: ① The line segment is straight; ② It has two endpoints; ③ The length of the line segment can be measured.

(2) How to draw a line segment: Start drawing from the scale 0 of the ruler. If you need to draw a line segment that is several centimeters long, draw it to a few centimeters of the ruler.

6． Judgment of length

To determine the height or length of an object, first, look at the number in front of the unit, and second, use the correct unit. When the object is relatively long, it is more appropriate to use "meter" as the unit; when it is shorter, it is more appropriate to use "centimeter" as the unit.

Length unit PPT, part 2: analysis of typical examples

Example 1: Two iron bars with a length of 8 cm are welded into one long iron bar. The joint (as shown below) is 3 cm. How many centimeters is the length of the welded iron bar?

Idea analysis:

Let students first understand the meaning of the question with the help of visual diagrams, and then solve the problem, paying attention to the diversity of problem-solving strategies. Method one: first find the length of the upper one after removing the welded part, and then add the length of the lower iron bar; method two: first find the total length of the two iron bars, and then subtract the length of the welded part.

Standard answer:

Method 1: 8-3=5 (cm), 5+8=13 (cm).

Method 2: 8+8=16 (cm), 16-3=13 (cm).

Example 2: Mom bought 1 meter of cloth and used 30 centimeters to make a skirt for Xiaolan. How many centimeters of cloth are left?

Idea analysis:

Subtract the cloth used to make Xiaolan's skirt from the total length of the cloth, which is the remaining cloth. To answer this question, you need to unify the units first and then calculate.

Standard answer:

1 meter = 100 cm 100-30 = 70 (cm)

Keywords: Free download of second-grade mathematics PPT courseware from the People's Education Press, length unit PPT download, .PPT format;

For more information about the "Unit of Length" PPT courseware, please click the Unit of Length PPT tab.

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Update Time: 2024-10-01

This template belongs to Mathematics courseware People's Education Press Second Grade Mathematics Volume 1 industry PPT template

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