Chapter 27: Add and Subtract Decimals

Lesson 1: Round Decimals. Objective: To round decimals using rounding rules and number lines.

Lesson 2: Estimate Decimals Sums and Differences. Objective: To estimate decimal sums and differences.

Lesson 3: Add Decimals. Objective: To write sums of decimals.

Lesson 4: Subtract Decimals. Objective: To write differences of decimals.

Lesson 5: Add and Subtract Decimals and Money. Objective: To cwrite sums and differences of decimals and money.

Lesson 6: Problem Solving Strategy: Evaluate Reasonableness of Answers. Objective: To use the problem solving strategy *evaluate reasonableness of answers.*

Vocabulary: tenth, hundredth, decimal, digit, round, number line, decimal point, regrouping, equivalent decimals

**tenth:** one of ten equal parts

**hundredth:** one of one hundred equal parts

**decimal:** a number with one or more digits to the right of a decimal point

**digit: **any one of ten symbols 0, 1, 2, 3, 4, 5, 6, 7, 8, or 9 used to write numbers

**round: **replace a number with a number that tells about how many or how much

**number line: **a line with equally spaced marks named by numbers

**mixed number: **an amount written as a whole number and a fraction

**decimal point:** the mark in a decimal number that separates the ones and the tenths place

**regrouping: **exchanging amounts of equal value when renaming a number

**equivalent decimals: **two or more decimals that name the same amount

Rounding Help:

**Rounding Rap**

Mark the place. Look to the right. 4 or less are out of sight. 5 and up will buy one more before they too are out the door. In those empty right-hand spaces, zeros keep the proper places.

Estimating and rounding:

http://www.math.com/school/subject1/lessons/S1U1L3GL.html

Rounding Whole Numbers: http://www.basic-mathematics.com/rounding-whole-numbers.html

Our textbook website: www.harcourtschool.com

Some good practice websites:

http://www.gamequarium.com/placevalue.html

http://www.softschools.com/math/games/

www.multiplication.com

www.funbrain.com