Math Study Guide

This was passed out last week, but I thought I would post it just in case!

Unit 2 Study Guide

This unit focuses on addition and subtraction word and number problems.  Please practice the following concepts with your child before our test on Tuesday, December 6, 2011. 

Addition:  Remember to regroup your place values when you are adding multi-digit numbers.  Regroup TO the LEFT. 

Subtraction:  Remember to regroup your place values when you are subtracting multi-digit numbers.  Regroup FROM the LEFT.

Commutative Property:  Addition can be done in any order.

       Example:  3+9+6 = 9+6+3

Inequalities:  When two equations do not equal one another we use the < (less than) or > (greater than) sign.

       Example:  8+9 > 8+3          8 x 9 > 8 x 3

Equalities:  Using an = or = sign to show if an equation is equal.

       Example:  8+9 = 9+8                 8 x 9 = 9 x 9

                   8+8+8+8 = 8 x 4          2+2+2+3 = 2 x 4

Break Apart Drawings:  These help us see that addition and subtraction are the inverse of one another.  2 addends equal our total.

Place Value:  Know the name of the place value of each number.

       Example:  777,298,433

7 hundred millions  (700,000,000)

7 ten millions  (70,000,000)

7 millions thousands  (7,000,000)

2 hundred thousands  (200,000)

9 ten thousands  (90,000)

8 thousands  (8,000)

4 hundreds  (400)

3 tens  (30)

3 ones  (3)

Writing Numbers:  Know the different ways to express numbers.

      

       Examples: 

Standard Form:  7,349

Expanded Form: 7,000 + 300 + 40 + 9

Word Form:  Seven thousand three hundred forty nine

Write Equations/Solve for the unknown variable:  Given word problems be able to determine whether or not they are addition or subtraction and what number is missing.  (Using break-apart drawings is very helpful to solve these!!!!) 

       Example:  Henry walked for 90 minutes on the weekend.  He walked for a total of 140 minutes for the week.  How many minutes did he walk on the weekdays? 

       Solution:  90 + x = 140        140 – 90 = 50 

                   Henry walked 50 minutes on the weekdays.

Comparison bars:  These help us compare numbers in word problems.

       Example:  At the zoo there are 12 lions.  There are 9 more tigers than lions.  How many tigers are at the zoo?

Multi-step word problems:  Understand when there is more than one operation that is needed to solve a problem. 

       Example:  Miguel gave the clerk two $20 bills for a hat that cost $16.50 and a shirt that cost $12.00.  How much change should Miguel receive? 

Step 1:  Two $20 bills = $40.00

Step 2:  How much did he spend on his items altogether?  16.50+12.00= 28.50

Step 3:  Set up an equation to show how much change he should get back.  40.00 – 28.50 = $11.50

Rounding:  Know how to round numbers to the place value given. First, underline the place value that you are looking at.  Then, draw an arrow to the number to the right.  Ask yourself if that number is 5 or higher or lower than 5.  If it is 5 or higher round up and change the rest of the number to the right to zeros.  If it is 4 or lower then round down and change the number to the right to zeros.

       Example:

Round 237 to the nearest ten:  240

Round 87,938 to the nearest thousand:  88,000

Know your multiplication and addition doubles!!  You will be tested on these!!

Ex:   2 x 2 =     3 + 3 =     4 x 4 =

       2 +2 =      3 x 3 =     4 + 4 =