Уроки математики и физики (RU + UA)

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вторник, 2 февраля 2016 г.

Lesson 1. Writing numbers

Place value tells you what each digit in a namber means. The value of the digit depends on the place it occupies.

Place Value of 100s

Numbers have digits. Place value helps you know what each digit stands for.

EXAMPLE:

Each digit in the number 111 has its own value.

EXAMPLE:

In the number 373, the 3 in the hundreds place, the 7 is the tens place, and the 5 is in the ones place. So 375 means 3 handreds + 7 tens + 5 onts.

Place Value of 1,000s

Some numbers have 4 digits.

EXAMPLE:

Each digit in the number 1,132 has its own value.

Place Value of 100,000s

You can write numbers that have 6 digits.

EXAMPLE:

Each digit in the number 763,285 has its own value.
You can use a place-value chart to help you tell the value of a digit in a number.

EXAMPLE:
This number is 493,286. The 2 is in the hundreds place. The 9 is in the ten thousands place.

USE A PLACE-VALUE CHART

EXAMPLE:

This place-value chart shows the place occupied by all the digits in the number 784,234,941.
In this number, the digit 7 is the hundred millions place, the digit 8 is in the ten millions place, and so on. Places are organized into periods, or groups of thee. A long string of digits is hard to read, so periods are separated by commas.

NUMBER FORMS

You can write numbers in different ways. There free three ways to write numbers. You can use standard form, expanded form, and word form.
  
Standard Form:

8,297,345.

Expanded Form:

(8×1,000,000) + (2×100,000) + (9×10,000) + (7×1,000) + (3×100) + (4×10) + (5×1).

Word Form:

Eight million, two hundred ninety-seven thousand, three hundred forty-five.
The value of a digit changes when its place in a number changes. You can multiply of divide to determine the value.

EXAMPLE:

In 700, the 7 has a value of 700. Move the 7 one place to the right. What is the value of the digit now? You can use a place value chart to find the value.
You can also divide by 10 to find the value: 

 700 ÷ 10 = 70. 

 The 7 has a value of 70.
EXAMPLE:

In 942, the 9 has a value of 900. Move the 9 one place to the left. What is the value of the digit now? You can use a place value chart to find the value.
You can also multiply by 10 to find the value:

900 × 10 = 9,000.

The 9 has a value of 9,000.
Don’t forget the comma after the millions place and the thousands place. Starting at the right, count every three digits to the left and add a comma.

Tasks to the lesson 1
Other lessons:
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