Chapter 2_Lessons 1-15 Study Topics
Lesson 2-1: More than Two Addends
 To use the strategies Group Tens and/or Doubles and Count On to add more than two addends
Textbook pg. 64-65
6
4
+ 5
15
10
10 + 5 = 15
**Remember: The Commutative Property of Addition states that changing the order of adding the addends
does not change the sum. Look for tens and doubles. **
Lesson 2-2: Missing Addends
 To find missing addends
Example:
3+ ?=7
7–3=4
So, 3 + 4 = 7
**Remember: Addition and subtraction are inverse operations. Addition “undoes” subtraction and
subtraction “undoes” addition.
Lesson 2-3: Add: No Regrouping
 To estimate sums using front-end estimation
 To add 2- and 3-digit numbers with no regrouping.
Example:
Find the sum then use front-end estimation.
Front-End Estimation
753
753
Add the front digits.
+ 106
+ 106
Then write 0’s for the
859
800
other digits.
Lessons 2-4: Estimate Sums
 To use rounding to estimate sums to the nearest ten or hundred and to the nearest ten cents or dollar.
**Remember rounding rule: 5 or more you raise the score (round up)
4 or less you let it rest (round down)
Lesson 2-5: Add with Regrouping
 To add 2-digit numbers and money amounts with regrouping.
Chapter 2_Lessons 1-15 Study Topics
**Remember: When there are more than 9 ones, regroup. **
Example:
Find the sum then use rounding to estimate.
1
Estimate by rounding
75
80
+ 26
+ 30
101
about 110
Lesson 2-9: Three-Digit Addition
 To add 3-digt numbers and money amounts, regrouping ones (pennies) or tens (dimes)
Example:
Estimate by rounding. Then add
Check:
7 12
1
677
+ 151
828
700
+200
900
828
- 151
677
Lesson 2-11: Mental Math
 To add numbers mentally.
Associative Property: changing the grouping of the addends does not change the sum.
Example: **Break apart numbers to find tens. **
76 + 25 = _______
(70 + 6) + (20 + 5)
90 + 11 = 101
Commutative Property: changing the order of the addends does not change the sum.
64 + 22 + 33= ________
33 + 22 + 64 = _______
22 + 64 + 33= _______
Lesson 2-13: Three or More Addends
 To add three or more 3-digit addends including money amounts, with multiple regroupings.
Lesson 2-14: Add Larger Numbers
 To add 4-digit numbers and money amounts, with regrouping.
Chapter 2_Lessons 1-15 Study Topics
Lesson 2-15: Problem Solving Strategy
 To solve problems by substituting simpler numbers.
Example:
Julia flew 425 miles to a layover in Texas. The she flew 215 miles farther. How far did she fly in all?
**Use the “Pencil Problem Solving Strategy” to help you solve word problems. **
425 + 215 = 640 miles