Comparing and Ordering Decimals When Will I Ever Do That???!!!

McDonald’s Menu…. I’m Lovin It!! Double Cheeseburger: $.99 Double Cheeseburger: $.99 Big Mac Value Meal: $ 4.79 Big Mac Value Meal: $ 4.79 Chicken McNuggetts Meal: $ 3.80 Chicken McNuggetts Meal: $ 3.80 Small Drink: $.99 Small Drink: $.99 McFlurry: $ 1.97 McFlurry: $ 1.97 Salad: $ 4.80 Salad: $ Cheeseburger Meal: $ Cheeseburger Meal: $ 3.70 Ice Cream Cone: $.87 Ice Cream Cone: $.87

Order Up! Least Expensive to Most Expensive Ice Cream Cone.87 Ice Cream Cone.87 Double Cheeseburger:.99 Double Cheeseburger:.99 Small Soft Drink:.99 Small Soft Drink:.99 McFlurry: 1.97 McFlurry: Cheeseburger Meal: Cheeseburger Meal: 3.70 Chicken McNuggetts Meal: 3.80 Chicken McNuggetts Meal: 3.80 Big Mac Value Meal: 4.79 Big Mac Value Meal: 4.79 Chicken Salad: 4.80 Chicken Salad: 4.80

What Do I Mean Compare Decimals? When we compare we use terms such as: When we compare we use terms such as: Less than < Less than < Greater than > Greater than > Equal to = Equal to = Comparing decimals is similar to comparing whole numbers. Comparing decimals is similar to comparing whole numbers. 45<47 45<47 150> >105 When we compare decimals we use place value or a number line. When we compare decimals we use place value or a number line.

Place Value 1,

Compare Sara’s score with Danny’s score. Compare Sara’s score with Danny’s score. 1. Line Up Decimal Points Sara: 42.1 Danny: Start at the left and find the first place where the digits differ. Compare the digits 1<5 42.1<42.5 This means Sara’s score was lower than Danny’s score. Sara42.1 Danny42.5 Ross42.0 Bethany40.7 Jacob46.1 Relay Race Results

Let’s Try Using A Number Line Sara42.1 Danny42.5 Ross42.0 Bethany40.7 Jacob Numbers to the right are greater than numbers to the left. Since 42.5 is to the right of 42.1 we have: 42.5>42.1

Annexing Zeros This means placing a zero to the right of the last digit in a decimal. This means placing a zero to the right of the last digit in a decimal Although we added a zero, the value of the decimal did not change!! Although we added a zero, the value of the decimal did not change!! Annexing or adding zeros is useful when ordering a group of decimals. Annexing or adding zeros is useful when ordering a group of decimals.

Ordering Decimals We can order decimals from least to greatest or we can order from greatest to least. We can order decimals from least to greatest or we can order from greatest to least. Let’s try an example: Let’s try an example: Order 15, 14.95, 15.8, and from least to greatest Order 15, 14.95, 15.8, and from least to greatest

First, line up the decimal points First, line up the decimal points , 14.95, 15.8, 15.01

Next, annex zeros so that each number has the same number of decimal places Next, annex zeros so that each number has the same number of decimal places

15, 14.95, 15.8, Finally, use place value to compare the decimals. Always start from the left!! Finally, use place value to compare the decimals. Always start from the left!! , 15, 15.01, , 15, 15.01, 15.8

One More Example Order these numbers from greatest to least Order these numbers from greatest to least 35.06, 35.7, 35.5, , 35.7, 35.5,

Rounding Decimal Numbers Sometimes close enough is good enough!

Molly has $16 in her pocket She buys: 3 $1.89 each 3 $2.19 each 3 Large French $ $1.79 each Does she have enough money?

Gas costs $3.30 per gallon I’m running on empty and I have a 20 gallon tank on my truck…… About how much will it cost to fill up?

You have one hour to take a 50 question test. About how much time can you spend on each question? Close enough is good enough!

The rounding poem Find your number Look right next door 4 or less, just ignore 5 or more add one more! Write this poem down in your notes!

Rounding Whole Numbers Round 474 to the closest hundred. 474 Find your number Look right next door Four or less, just ignore Five or more, add one more

474 Rounded to the hundreds becomes 500 Round 474 to the closest 10’s 474 Just ignore - 470

What about decimal numbers The same rules (and poem) apply! Round to the closest hundredths Find your number Look right next door 4.17

Remember If you are asked to round to the nearest tenth…….your answer stops at the tenth place! Example: Round to the closest tenth would be 42.7

Special Case! Rounding a 9 Round to the closes hundredths Since there is a “9” in the hundredths place consider the tenth and hundredths together – 19 – do you leave it at 19 or move it to 20?

Round 4.95 to the closest tenth Since there is a “9” in the tenth spot consider the ones and tenths together…… should you leave it at 49 or move it to 50? 4.95 rounded to the nearest tenth is 5.0

Try these tenths Round to tenths: hundredths Round to hundredths