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Subtraction of natural numbers in memory

Source: licencja: CC 0.

Odejmowanie pamięciowe liczb naturalnych

Learning objectives

You will learn the subtraction properties and you will learn different methods of memory subtraction of two‑digit natural numbers.

Learning effect

  • You subtract two‑digit natural numbers in your memory.

Try to remind what subtractionsubtractionsubtraction of natural numbers is about, what the numbers that we subtract and the result of subtractionsubtractionsubtraction are called.

Task 1
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nagranie abstraktu

Open the Interactive illustration and see what the numbers in the subtractionsubtractionsubtraction are called.

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Ilustracja interaktywna przedstawia zapis działania 20 odjąć 8 równa się 12. Strzałka wskazuje 20, strzałka wskazuje 8, 20 odjąć 2 wzięte w klamrę , strzałka wskazuje 12. Na ilustracji widoczne są numery, a na nich podpisy. 1. minuend {audio}, 2. difference {audio}, 3. subtrahend {audio}, 4. difference {audio}.
Subtraction of numbers
Source: GroMar, licencja: CC BY 3.0.
Task 2
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nagranie abstraktu

On the basis of Graph 1, answer the question: How can you check if the subtractionsubtractionsubtraction has been carried out correctly? Write down your conclusions.

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Source: GroMar, licencja: CC BY 3.0.
Task 3
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nagranie abstraktu

Using the example above, complete the graphs and blank spaces next to the graphs.

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Source: GroMar, licencja: CC BY 3.0.
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Source: GroMar, licencja: CC BY 3.0.
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Source: GroMar, licencja: CC BY 3.0.
Task 4
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nagranie abstraktu

Make calculations. Then write the answer to the question: What is the difference of the numbers if the subtrahend is equal the minuend?

  1. 7 - 7,

  2. 20 - 20,

  3. 15 - 15,

  4. 35 - 35.

Task 5
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nagranie abstraktu

In the dotted blank spaces, enter the appropriate number. Then write the answer to the question: What number is the subtrahend if the minuend is equal the difference?

  1. 7 - ..... = 7,

  2. 20 - .... = 20,

  3. 15 - .... = 15,

  4. 35 - .... = 35.

Conclusions:

  • The correctness of the subtractionsubtractionsubtraction can be checked by addingaddingadding.

  • If the subtrahendsubtrahendsubtrahend is equal to the minuendminuendminuend, then the differencedifferencedifference is zero.

  • If the subtrahendsubtrahendsubtrahend is equal to zero, then the differencedifferencedifference is equal to the minuendminuendminuend.

Task 6
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nagranie abstraktu

Analyze the following method of subtracting two two‑digit numbers in memory.

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Source: GroMar, licencja: CC BY 3.0.
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nagranie abstraktu

Using the method presented in the figure, calculate the given differences:

  1. 38 - 25,

  2. 87 - 56,

  3. 59 - 22,

  4. 76 - 65.

Task 7
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nagranie abstraktu

Analyze the following method of subtracting two two‑digit numbers in memory.

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Source: GroMar, licencja: CC BY 3.0.
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nagranie abstraktu

Using the method presented in the figure, calculate the given differences:

  1. 38 - 29,

  2. 54 - 36,

  3. 73 - 25,

  4. 54 - 18.

Task 8
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nagranie abstraktu

Analyze the following method of subtracting two two‑digit numbers in memory.

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Source: GroMar, licencja: CC BY 3.0.
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nagranie abstraktu

Using the method presented in the figure, calculate the given differences:

  1. 38 - 29,

  2. 54 - 36,

  3. 73 - 25,

  4. 54 - 18.

Task 9
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nagranie abstraktu

Calculate the differences by any method and check the result by adding:

  1. 90 - 79,

  2. 91 - 56,

  3. 46 - 27,

  4. 54 - 39,

  5. 83 - 36,

  6. 63 - 56.

Task 10
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nagranie abstraktu

Solve the following word problems, using the subtraction methods learned in the lesson:

a) There were 35 tulips in the vase, a mother took 19 flowers. How many tulips remained in the vase?

b) Tomek had 50 zloty. He bought a book for 26 zloty. How much change did he receive?

Task 11
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nagranie abstraktu

An extra task:

How did the differencedifferencedifference change if the minuendminuendminuend decreased by 11, and the subtrahendsubtrahendsubtrahend increased by 6?

Do the revision exercises.

Remember:

  • The correctness of the subtractionsubtractionsubtraction can be checked by addingaddingadding.

  • If the subtrahendsubtrahendsubtrahend is equal to the minuendminuendminuend, then the differencedifferencedifference is zero.

  • If the subtrahendsubtrahendsubtrahend is equal to zero, then the differencedifferencedifference is equal to the minuendminuendminuend.

Exercises

Exercise 1
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Wersja alternatywna ćwiczenia: Determine which sentences are true. Możliwe odpowiedzi: 1. To check the correctness of the subtraction, add the difference to the subtrahend., 2. If we subtract zero from the minuend, the difference is equal to the subtrahend., 3. If we add a subtrahend to the difference, we will get a minuend., 4. If the minuend is equal to the subtrahend, the difference obtained is equal to zero.
zadanie
Source: GroMar, licencja: CC BY 3.0.
Exercise 2

Fill in the fields marked with letters so that the result in the green field is always equal to 16.

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Source: GroMar, licencja: CC BY 3.0.
Exercise 3

Find numbers a, b and c. Check if the results are correct.

  1. 25 - a = 14,

  2. b - 42 = 54,

  3. 76 - 38 = c.

Write down the values of numbers a, b and c with words in English.

Exercise 4
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Wersja alternatywna ćwiczenia: Indicate which pairs of expressions or words are translated correctly. Możliwe odpowiedzi: 1. różnica - difference, 2. odjemna - minuend, 3. odjemnik - subtrahend, 4. odejmowanie - subtraction, 5. sprawdzenie - adding, 6. poprawność odejmowania - checking the result
zadanie
Source: GroMar, licencja: CC BY 3.0.
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Interaktywna gra, polegająca na łączeniu wyrazów w pary w ciągu jednej minuty. Czas zaczyna upływać wraz z rozpoczęciem gry. Jeden ruch to odkrywanie najpierw jednej potem drugiej karty z wyrazem. Każdy wyraz jest odczytywany. Kolejny ruch to odkrywanie trzeciej i czwartej karty. W ten sposób odsłuchasz wszystkie wyrazy. Nawigacja z poziomu klawiatury za pomocą strzałek, odsłuchiwanie wyrazów enterem lub spacją. Znajdź wszystkie pary wyrazów.
Source: Zespół autorski Politechniki Łódzkiej, licencja: CC BY 3.0.

Glossary

adding
adding

dodawanie

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wymowa w języku angielskim: adding
checking the result
checking the result

sprawdzenie

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wymowa w języku angielskim: checking the result
correctness of subtraction
correctness of subtraction

poprawność odejmowania

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wymowa w języku angielskim: correctness of subtraction
difference
difference

różnica – wynik odejmowania dwóch liczb

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wymowa w języku angielskim: difference
minuend
minuend

odjemna - liczba od której odejmujemy

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wymowa w języku angielskim: minuend
subtraction
subtraction

odejmowanie

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wymowa w języku angielskim: subtraction
subtrahend
subtrahend

odjemnik – liczba, którą odejmujemy

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wymowa w języku angielskim: subtrahend
sum / total
sum / total

suma

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wymowa w języku angielskim: sum / total

Keywords

differencedifferencedifference - result of subtraction of two numbers

minuendminuendminuend - a number which you subtract from

subtrahendsubtrahendsubtrahend - a number which you subtract