Unit 2: Decimals. Thousands Hundreds Tens Ones Tenths Hundredths Thousandths Ten thousandths

Transcription

1 Unit 2: Decimals Decimals are a part of a whole (just like fractions) PLACE VALUE Thousands Hundreds Tens Ones Tenths Hundredths Thousandths Ten thousandths What is the decimal point for? To determine the position of the ones place the ones position is left of the decimal 35

2 Practice: What is the position of the 8 in each of the following? Ordering & Comparing: First look at the whole numbers Look at the tenths position the largest digit is the larger number Then look at the hundredths position, and so forth Example: Order from greatest to least: No whole #s Greatest to Least:

3 Practice: Place <, >, or = Place in order of least to greatest: ,,,,,, ROUNDING: Step 1: Underline the digit to be rounded Step 2: Write the 2 possible rounding positions Step 3: Follow the rule: The digit to the right is a 4 or less, the underlined digit stays the same The digit to the right is a 5 or greater, the underlined digit becomes one greater All the remaining digits are replaced by zero Example: round to nearest tenths the digit to the right of 0 is a 9 = Practice: round to nearest tenths round to nearest hundredths round to nearest ones Practice: 37

4 Order the following least to greatest ,,, Put <, >, or = Put the following on a number line The cashier at the restaurant is working with a calculator to get the total amount of each bill after he calculates the tax. He is confused and doesn t know what to tell the customers what they owe because there are too many numbers. Please help him decide how much each customer must pay. Customer 1: $ Customer 2: $ Customer 3: $

5 What is the position of the 6 in each number? Circle which number is greater between the pairs. a) 4.15 and 4.16 b) and c) and 24.5 d) and e) and What about time? Place in order from longest to shortest time: (distance race) 2:33 3:03 3:45 2: 29 2:59 3:19,,,,, Place in order from the slowest to fastest time: 5:003 5:030 5:303 5:330 5:033 4:599,,,,, Adding and Subtracting Decimals: 39

6 Line up the decimals and fill in empty space after the decimal with zeros. Example: Example: Practice: Estimate, and then find the sum. a) b) c) d) Estimate, and then find the difference. 40

7 a) b) c) d) Find the missing number. a) = b) 43.1 = c) = 38.1 d) 5.08 = 14.7 Answer the following questions using the decimals from the box. a) Use 2 decimals whose sum is b) Use 2 decimals whose difference is c) Use 3 decimals whose sum is Multiplying Decimals 41

8 Multiply like whole numbers Count the digits after the decimal for each number Starting from the end of the answer, move left the number of spaces you just counted Place the decimal Example: x x 79 3 digits after the decimal = Practice: Find the product x x x x 0.7 Scott worked 24 hours last week. He makes $9.55 per hour. He got $44.50 in tips. How much money did Scott make last week? Dividing Decimals 42

9 If there is no decimal outside (the divisor), divide like whole numbers, and when you get to the decimal, put it up, and then continue Example: You are usually asked to go to 3 places after Practice: Find the quotient

10 If there is a decimal outside (the divisor), move it until the number is whole, and move the decimal inside the same number of spaces. If there are less spaces inside, add zeros. Remember, there are no remainders. 225 Example: = Practice: Find the quotient Blake stacked 12 blocks which measured 45.6 centimetres. What is the height of each block? 44

11 Order of Operations and Decimals: follow the rules of BEDMAS Practice: x x ( ) ( ) ( ) 9.8 x (4.5 ( ) ) [ ( )] 34.2 ( ) 45

12 Decimal Practice: Find the missing number. a) 5 x = 45 b) 12 = 3.45 c) 14.3 = 5.2 d) 3.2 x = The service elevator can lift a maximum of 650 kg. A shipment of the following just arrived. Can all the boxes be delivered in one trip on the elevator? Explain your reasoning kg kg 89.3 kg 68.3 kg kg kg Anne stops to get gas at 97.4 cents per litre. Her total cost was $ On her way home she notices the price of gas at another station was 1.6 cents cheaper. Anne is upset about the money she could have saved. How much could she have saved? 46

13 Extra Practice: NO CALCULATOR x