Form 2 Unit 1 Lesson 1: Numbers (Revision)
Objectives
At the end of this lesson, students should be able to:
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Order numbers in ascending or descending order.
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Add and subtract whole numbers and decimal numbers.
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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
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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
