Decimals

Place Value Review - *Whole* 9,587,541,645,315 trillions hundred billions ten billions billions hundred millions ten millions millions hundred thousands ten thousands thousands hundreds tens ones Each position is 10 times bigger than the last!

Decimal Place Value – *Parts* 10.354869327543 DECIMAL POINT tenths hundredths thousandths ten thousandths hundred thousandths millionths ten millionths hundred millionths billionths ten billionths hundred billionths trillionths Each position gets 10 times smaller!

Decimal Place Value Chart

Types of Decimals Terminating Decimal- a decimal that ends ex: 1.23 16.5 7.156 Repeating Decimal- a decimal that continues on forever with one or more digits repeating a pattern ex: .33333… 2.83333… 5.090909… aka .3 aka 2.83 aka 5.09

Rounding Decimals 1. Find the place value you want to round to (the “rounding digit”) If the number to the right of “the rounding digit” is less than 5, make all numbers to the right of the rounding digit zeros If the number is greater than 5, add one to the rounding digit and then everything to the right becomes zero ex: Round 54.9874 to the nearest hundredth 8 1. Find hundredth 2. Is the number to the right bigger than 5? 3. Yes. Then Round 8 up to 9 and the following numbers go away 54.99 Is the answer

Adding & Subtracting Decimals Line up the decimal points and add or subtract. 5.02 + 6.325 ADD ex. 5.02 + 6.325 . 11 3 4 5 12 SUBTRACT ex. 12.45 - 7.3 12.45 - _7.3_ / / . 5 1 5

iPad Activity – Adding Decimals http://www.coolmath.com/prealgebra/02-decimals/decimals-cruncher/addition

Use Distributive Property to solve mentally! Multiply Decimals Ignore the decimal point Multiply the whole numbers as you normally would. ex. 6 • 5.3 6 • 53 _____ ____ 6 • 50 + 6 • 3 318 300 + 18 Use Distributive Property to solve mentally! 3. Count how many decimal places you started with 4. Keep that same number of decimal places in the answer ex. 6 • 5.3 318 31.8 One decimal place One decimal place

Multiply Decimals Practice 236 x 25 1180 +4720 5900 ex. 0.25 x 0.0236 5900 . 2 places 4 places 6 places .0059

More Multiplication Practice 5 x 0.25 3 x 1.4 8 x 5.1 3.20 x 7 5.33 x 6.2 1.25 4.2 40.8 22.4 33.046

Divide Decimals by whole numbers ex. 16.25 ÷5 . 5 16.25 1. Use long division 2. Bring decimal point up into the answer. . 3. Solve 3 2 5 5 16.25 3.25 15 1 2 10 2 5 25

Divide Decimals by decimals ex. 18.6 ÷ 6.2 6.2 18.6 1. Use long division 2. Make the divisor a whole number 6.2 62. 3. Move dividend decimal the same number of spaces 18.6 186. 4. Solve using long division 3 . 3 62. 186. 186 5. Bring decimal point up into the answer.

Decimal means “Based on 10” After every whole number, there is a decimal point. ex. 5 5.0 or 5.00 or 5.0000000 etc. But it all means “5” Multiply by 10: the decimal point moves right, making the number larger. ex. 12 • 10 12.0 = 120. = 120 ex. 12.325 • 10 12.325 = 123.25 Divide by 10: the decimal point moves left, making the number smaller. ex. 12 ÷ 10 12.0 = 1.20 = 1.2 ex. 12.325 ÷ 10 12.325 = 1.2325