Form 2 Unit 1 Lesson 1: Numbers (Revision)

Objectives

At the end of this lesson, students should be able to:

  • Order numbers in ascending or descending order.

  • Add and subtract whole numbers and decimal numbers.    

  • Multiply and divide whole numbers and decimal numbers.

Ordering Numbers

Ordering numbers means to organize numbers in a particular pattern, ascending or descending.

Ascending order

Numbers are in ascending order when they are arranged from the smallest to the largest number. Example: 157, 324, 879, 999, 1055

Descending order

Numbers are in descending order when they are arranged from the largest to the smallest number. Example: 391, 245, 167, 38.

 

Example 1

  1. Write these measures in descending order; 2m, 60cm, 800mm, 180cm, 0.75m

Solution

First change all the measurements into the same unit.

The solution to the question becomes 2 m, 180 cm, 800 mm, 0.75 m and 60 cm in descending order.

Adding Whole Numbers and Decimal Numbers

 

Example 1:  21376 + 15 + 2 + 96498.

Note: Arrange the numbers vertically and add. (Make sure the digits are aligned in their correct place value.)

Solution:

Example 2: 144 + 2.18 +9007 + 16.345

Solution

 

Subtracting Whole Numbers and Decimal Numbers

 

Example 1:   91234 – 698

Note: Arrange the numbers vertically and subtract. (Make sure the digits are aligned in their correct place value.)

Solution

Example 2:   5368 – 8.329

Solution

Multiplying Whole Numbers and Decimal Numbers

 

Example 1:   846 × 79

Solution

Example 2:   237.5 × 4.36

Solution

Dividing Whole Numbers and Decimal Numbers

Example 1: 56232÷9

Solution

Example 2

109.94 ÷ 23

Solution

Example 3:   717.822 ÷ 1.26

Solution

Note: When the divisor is a decimal number, first you have to multiply the divisor and the dividend by a multiple of 10 which will make the divisor a whole number.  If the divisor has 1 decimal place, multiply both numbers by 10.  If it has 2 decimal places, multiply them by 100 and if it has 3 decimal places, multiply them by 1000. In this example, since the divisor has 2 decimal places, multiply them by 100 before you divide. As long as you multiply both numbers by the same number, you have not changed the question.

717.822 ÷ 1.26 = 717.822 × 100 ÷ 1.26 × 100

=71782.2 ÷ 126

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