Review of natural numbers

### 1.1. Solving textbook exercises on pages 147, 148

**Lesson 1 Textbook page 147**

a) Read the following numbers:

70815; 975 806; 5 723 600; 472 036 953.

b) State the value of the digit 5 in each of the numbers above.

__Solution guide:__

a) Number 70815, read as: seventy thousand eight hundred and fifteen,

Number 975 806, read as: nine hundred and seventy-five thousand eight hundred and six.

Number 5 723 600, read: five million seven hundred twenty three thousand six hundred.

Number 472 036 953, read: four hundred and seventy-two million zero hundred thirty six thousand nine hundred fifty-three.

b) The digit 5 out of 70815 belongs to the unit row, so the value is 5 units.

The digit 5 out of 975 806 is in the thousands, so the value is 5000.

The digit 5 out of 5 723 600 is in the millions, so the value is 5 000 000.

The digit 5 out of 472 036 953 belongs to the tens, so the value is 50.

Lesson 2 Textbook page 147

Write the correct number in the dot to get:

a) Three consecutive natural numbers:

998; 999; … …; 8000; 8001. 66 665; …; 66 667.

b) Three consecutive even numbers:

98; 100; … 996; 998; … ….; 3000; 3002.

c) Three consecutive odd numbers

77; 79; … 299; …; 303. …; 2001; 2003.

__Solution guide:__

a) 998; 999; 1000 7999; 8000; 8001. 66 665; 66 666; 66 667.

b) 98; 100; 102 996; 998;1000 2998; 3000; 3002.

c) 77; 79; 81 299; 301; 303. 1999; 2001; 2003.

Lesson 3 Textbook page 147

Put >, <, = in the dot:

1000…997

53796…53800

6987…10087

217690…217689

7500:10…750

68400…684×100

__Solution guide:__

We have:

1000 > 997

53796 > 53800

6987 < 10087

217690 < 217689

7500:10 = 750

68400 = 684×100

Lesson 4 Textbook page 147

Write the following numbers in order:

a) From baby to adult: 4856; 3999; 5486; 5468.

b) From big to small: 2763; 2736; 3726; 3762.

__Solution guide:__

a) We have: 3999 < 4856 < 5468 < 5686.

So the numbers arranged in order from smallest to largest are: 3999; 4856; 5468; 5686.

b) We have: 3762 > 3726 > 2763 > 2736.

So the numbers arranged in order from largest to smallest are: 3762; 3726; 2763; 2736.

Lesson 5 Textbook page 148

Find the appropriate digit so that when we write in the dot we get:

a) …43 is divisible by 3;

b) 2…7 is divisible by 9;

c) 81… is divisible by both 2 and 5;

d) 46… divisible by both 3 and 5.

__Solution guide:__

a) For the number …43 to be divisible by 3 then ….+ 4 + 3 = …. + 7 is divisible by 3.

So you can write in the dot one of the following numbers: 2, 5, 8.

b) Similarly, for the number 2…7 to be divisible by 9, then 2 + ….+ 7 = 9 +…. is divisible by 9.

So you can write 0 or 9 in the dot.

c) For 81… to be divisible by both 2 and 5, then … must be 0.

So we write 0 in the dot.

d) 46…. is divisible by 5 so …. can be 0 or 5

– If … is 0 we have the number 460.

The number 460 has the sum of its digits 4 + 6 + 0 = 10 . Since 10 is not divisible by 3, the number 460 is not divisible by 3 (Type).

– If … is 5 we have the number 465.

The number 465 has the sum of its digits 4 + 6 + 5 = 15 . Since 15 is divisible by 3, the number 465 is divisible by 3 (Choose).

So we write the digit 5 in the dot.

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