Topicmdf193cf95c4e5232_1528449000663_0Topic

Long subtraction of natural numberslong subtraction of natural numbersLong subtraction of natural numbers

Levelmdf193cf95c4e5232_1528449084556_0Level

Second

Core curriculummdf193cf95c4e5232_1528449076687_0Core curriculum

Calculations on natural numbersnatural numbersnatural numbers. The student:

2) does addition and subtractionsubtractionsubtraction using the long method as well as the calculator.

Timingmdf193cf95c4e5232_1528449068082_0Timing

45 minutes

General objectivemdf193cf95c4e5232_1528449523725_0General objective

Doing simple calculations mentally or using the long method in more difficult examples, using these abilities in practical situations.

Specific objectivesmdf193cf95c4e5232_1528449552113_0Specific objectives

1. Long subtraction of natural numberslong subtraction of natural numbersLong subtraction of natural numbers.

2. Applying long subtractionsubtractionsubtraction of natural numbersnatural numbersnatural numbers to do text exercises.

3. Communicating in English, developing basic mathematical, computer and scientific competences, developing learning skills.

Learning outcomesmdf193cf95c4e5232_1528450430307_0Learning outcomes

The student:

- does long subtractionsubtractionsubtraction of natural numbersnatural numbersnatural numbers,

- applies long subtraction of natural numberslong subtraction of natural numberslong subtraction of natural numbers to do text exercises.

Methodsmdf193cf95c4e5232_1528449534267_0Methods

1. Situational analysis.

2. Talking cards.

Forms of workmdf193cf95c4e5232_1528449514617_0Forms of work

1. Individual work.

2. Work in pairs.

Lesson stages

Introductionmdf193cf95c4e5232_1528450127855_0Introduction

Students revise various methods of mental subtraction of natural numbersnatural numbersnatural numbers.

They do subtractionsubtractionsubtraction using the calculator:

1. 1938 – 1894,

2. 1903 – 1867,

3. 5003 – 2177,

4. 9000 – 678.

Discussion:

- Do we always carry calculator with ourselves?

- Is it easy to make such calculations mentally?

The teacher informs students that during this class they will learn to subtract great numbers without using the calculator.

Proceduremdf193cf95c4e5232_1528446435040_0Procedure

Task
Students work individually, using computers. They open the Slideshow 1 and observe how we perform long subtraction of natural numberslong subtraction of natural numberslong subtraction of natural numbers. After having completed the exercise, they present results of their observations.

[Slideshow 1]

Conclusions:

- Long subtraction of natural numbers starts with writing numbers under one another, in such a way that ones are under ones, tens under tens, etc. We put a line under the numbers.
- Then we subtract ones and write the result under the line, in the place of ones. Then we subtract tens and write the result under the line, in the place of tens, etc.
- If in one of the rows the minuend is smaller than the subtrahend, we need to ‘carry’ 1 from the higher row, so that we can do the subtraction.mdf193cf95c4e5232_1527752263647_0- Long subtraction of natural numbers starts with writing numbers under one another, in such a way that ones are under ones, tens under tens, etc. We put a line under the numbers.
- Then we subtract ones and write the result under the line, in the place of ones. Then we subtract tens and write the result under the line, in the place of tens, etc.
- If in one of the rows the minuend is smaller than the subtrahend, we need to ‘carry’ 1 from the higher row, so that we can do the subtraction.

Task
Students work individually, using computers. They open the Slideshow 2 and observe how we perform long subtraction of natural numberslong subtraction of natural numberslong subtraction of natural numbers if in the minuendminuendminuend occurs zero.

[Slideshow 2]

Students work in pairs. After having completed the exercise, they exchange notebooks and verify their solutions using calculators.

Task
Do the long subtraction:

1. 862 – 541,

2. 1569 – 458,

3. 1483 – 1394,

4. 2500 – 158,

5. 3050 – 2605.

Task
Do the exercises by performing long subtractionsubtractionsubtraction. Give the answers:

a) Tomek got a new book. During first two days he read 150 pages of this book. How many pages does he have left if the whole book has 314 pages?

b) A TV costs 3799 zł and a phone 1560 zł. By how many złoty is the TV more expensive than the phone?

c) In 1683 king Jan III Sobieski won the Battle of Vienna. How many years has passed since that battle?

Task
Talking cards.

The teacher asks student show to verify solutions of subtractionsubtractionsubtraction without using the calculator. The teacher asks the students to write down the ideas on pieces of paper. The teacher collects them and reads students’ propositions.

The idea that should dominate:
- We can verify the result of subtraction by doing addition. By adding the difference to the subtrahend, we should obtain the minuend.mdf193cf95c4e5232_1527752256679_0The idea that should dominate:
- We can verify the result of subtraction by doing addition. By adding the difference to the subtrahend, we should obtain the minuend.

Example:

[Illustration 1]

Students work in pairs. After having completed the exercises, they exchange notebooks and verify the solutions of their calculations.

Task
Do the long subtraction:

1. 874 – 323,

2. 1876 – 765,

3. 1582 – 1495,

4. 6300 – 4321,

5. 4050 – 3504.

Task
Do the calculations using long subtractionsubtractionsubtraction:

1. 7000 – 2623 – 972,

2. 5043 – 2654 – 1236.

An extra task
What number should be inserted in the place of * so that the calculation is correct?

[Illustration 2]

Lesson summarymdf193cf95c4e5232_1528450119332_0Lesson summary

Students do the revision exercises.

Then together they sum‑up the classes, by formulating the conclusions to memorise:

- Long subtraction of natural numbers starts with writing numbers under one another, in such a way that ones are under ones, tens under tens, etc. We put a line under the numbers.
- Then we subtract ones and write the result under the line, in the place of ones. Then we subtract tens and write the result under the line, in the place of tens, etc.
- If in one of the rows the minuend is smaller than the subtrahend, we need to ‘carry’ 1 from the higher row, so that we can do the subtraction.mdf193cf95c4e5232_1527752263647_0- Long subtraction of natural numbers starts with writing numbers under one another, in such a way that ones are under ones, tens under tens, etc. We put a line under the numbers.
- Then we subtract ones and write the result under the line, in the place of ones. Then we subtract tens and write the result under the line, in the place of tens, etc.
- If in one of the rows the minuend is smaller than the subtrahend, we need to ‘carry’ 1 from the higher row, so that we can do the subtraction.

Selected words and expressions used in the lesson plan

differencedifferencedifference

hundreds rowhundreds rowhundreds row

long subtraction of natural numberslong subtraction of natural numberslong subtraction of natural numbers

minuendminuendminuend

natural numbersnatural numbersnatural numbers

ones rowones rowones row

subtractionsubtractionsubtraction

subtrahendsubtrahendsubtrahend

tens rowtens rowtens row

thousands rowthousands rowthousands row