Summation

### 1.1. Knowledge to remember

**a) 48352 + 21026 = ?**

*Add in order from right to left: *

- 2 plus 6 equals 8, write 8.
- 5 plus 2 equals 7, write 7.
- 3 plus 0 equals 3, write 3.
- 8 plus 1 equals 9, write 9.
- 4 plus 2 equals 6, write 6.

\(\begin{array}{l}

\underline { + \begin{array}{*{20}{c}}

{48352}\\

{21026}

\end{array}} \\

\,\,\,\,69378

\end{array}\)

48352 + 21026 = 69378

**b) 367859 + 541728 = ?**

*Add in order from right to left:*

- 9 plus 8 equals 17, write 7 remember 1.
- 5 plus 2 equals 8, add 1 equals 8, write 8
- 8 plus 7 equals 15, write 5 remember 1.
- 7 plus 1 equals 8, plus 1 equals 9 write 9.
- 6 plus 4 equals 10, write 0 and remember 1.
- 3 plus 5 equals 8, plus 1 equals 9, write 9.

\(\begin{array}{l}

\underline { + \begin{array}{*{20}{c}}

{367859}\\

{541728}

\end{array}} \\

\,\,\,\,909587

\end{array}\)

367859 + 541728 = 909587

### 1.2. Solving Textbook Exercises

**Lesson 1:** Calculate then calculate

a) 4682 + 2305 b) 2968 + 6524

5247 + 2741 3917 + 5267

**Solution guide:**

To add two natural numbers we can do the following:

- Write one term below the other such that the digits in the same row line up in the same column.
- Add the digits in each row in order from right to left, ie from units to tens, hundreds, thousands, … .

a)

\(\begin{array}{l}

\underline { + \begin{array}{*{20}{c}}

{4682}\\

{2305}

\end{array}} \\

\,\,\,\,6987

\end{array}\) \(\begin{array}{l}

\underline { + \begin{array}{*{20}{c}}

{5247}\\

{2741}

\end{array}} \\

\,\,\,\,7988

\end{array}\)

b)

\(\begin{array}{l}

\underline { + \begin{array}{*{20}{c}}

{2968}\\

{6524}

\end{array}} \\

\,\,\,\,9492

\end{array}\) \(\begin{array}{l}

\underline { + \begin{array}{*{20}{c}}

{3917}\\

{5267}

\end{array}} \\

\,\,\,\,9184

\end{array}\)

**Lesson 2: **Calculate

a) 4685 + 2347 b) 186954 + 247436

6084 + 8566 514625 + 82398

57969 + 814 793575 + 6425

__Solution guide:__

To add two natural numbers, we can do the following:

- Write one term below the other such that the digits in the same row line up in the same column.
- Add the digits in each row in order from right to left, ie from units to tens, hundreds, thousands, … .

Students self-calculated as in lesson 1, the results are as follows:

a) 4685 + 2347 = 7032

6084 + 8566 = 14660

57969 + 814 = 58510

b) 186954 + 247436 = 434390

514625 + 82398 = 597023

793575 + 6425 = 800000

**Lesson 3:** One district planted 325 164 timber trees and 60 830 fruit trees. How many trees can be planted in the district?

__Solution guide:__

Number of planted trees = number of timber trees + number of fruit trees.

*Solution*

The number of trees planted in the district is:

325 164 + 60 830 = 385994 (tree)

Answer: 385 994 trees.

**Lesson 4: **Find x

a) x – 363 = 975 ;

b) 207 + x = 815.

__Solution guide:__

Apply the rules:

- To find the number to be subtracted, we take the difference plus the minus number.
- To find the unknown term, subtract the known term from the sum

a) x – 363 = 975

x = 975 + 363

x = 1338

b) 207 + x = 815

x = 815 – 207

.

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