Chapter 5.1 - 5.4 Revision

1. Chapter 5.1 - 5.4 Revision Decimals The chapter Is about decimals, you learn about place value with decimals, how to estimate with decimal equation, how to convert fractions to decimals and how to add and subtract decimals. Chapter 5.1 Decimals and place value A decimal is a number which is expressed in the counting system that uses units of 10s. It is a fraction of a part using 10s as a base number. The value of the place of a digit in a numeral is known as Place Value. Samples What is the value of 1 in 78.518What is the value of 5 in 78.518 What is the value of 8 in 78.518 Answer: 1 hundredth Answer: 5 tenths Answer: 8 thousandth Solution: The number is 78.518 and Solution: The number is 78.518 and Solution: The number is 78.518 and 1 is in the hundredth column 5 is in the tenths column 8 is in the thousandth column

2. Chapter 5.2 Approximation and estimation Approximation and estimation is very important when dealing with decimals. That is because some decimals can never end, like this number 0.3333333333. the 3 could just keep on going in this example. Now this is where approximation comes in. Approximation can be achieved by rounding up or down. The rule of the thumb is to round up when the leading digit is greater than 5 else round down. For example – 7.26 is round up to 7.3 because 6 (the leading digit) is greater than 5. Samples Round off 9.28867 to 3 decimal places. Answer: 9.289 Solution: The leading number 6 is more than 5 so the number became 9.289 Round off 27.97428 to 2 decimals Places. Answer: 27.97 Solution: The leading number 4 is less than 5 so the number became 27.97 What is 6.98×5.38 Answer: 35 Solution: you round off 6.89 to the nearest unit which is 7. Then round off the 5.38 to the nearest unit which is 5. 7×5= 35

3. Chapter 5.3 Conversion of fractions to decimals Converting fractions to decimal is very easy. All you have to do is divide the numerator by the denominator. in a result if a number or a sequence of number repeats itself in a pattern then it is presented by putting a dot or line on the head. For example 0.66666 can be represented as 0.6 and if the number is something like 0.8989898989 then you can represent it as 0.89 Samples . Convert in a decimal Answer: 0.6 Solution: 3 Convert 5in a decimal Answer: 5.3 Solution: 5 is actually 5 + = 5 + 0.3 = 5.3 Convert in a decimal Answer: 0.7 Solution: 7

4. Chapter 5.4 Addition and subtraction of decimals Adding decimals and subtracting decimals is basically the same as adding and subtracting whole numbers. Samples What is the sum of 78.388,47.59 Answer: 125.987 Solution: 78.388+47.59=125.987 What is the sum of 9.4756,789.5 Answer: 789.9756 Solution: 9.4756+789.5= 789.9756 How much greater is 65.7 than 6.04 Answer: 59.66 Solution: 65.7-6.04=59.66

5. Now some revisionQuestions for Decimals Put these number in ascending order: 32.89, 763, 518.90, 6728, 26830.38 5980, 58730, 28684, 4026, 847 0.5980, 0.58730, 0.28684, 0.4026, 0.847 Find the value of : 6 in 782.26 9 in 839.72 3 in 7.793 Round off to 2 decimal places 6589.57839 3.4780 75.5740 Convert into decimal The sum of: 87.387,32.78 and 67.12 54.67,21.89 How much is: 67.890 greater than 9.65 20.79 greater than 19.20

6. Answers • 32.89, 518.90, 763, 6728, 26830.38 • 847, 4026, 5980, 28684, 58730 • 0.847, 0.5980, 0.58730, 0.4026, 0.28684 • 6 Tenth • 9 units • 3 thousandth • 6589.58 • 3.48 • 75.57 • 0.53 • 0.375 • 187.287 • 76.56 • 58.24 • 1.59