# Sums that Go Over to the Next Ten

This is a complete lesson with instruction and exercises about sums that "go over" or cross the next ten, meant for 2nd grade. First, students use visual models (base ten blocks) to add a single digit number and a two-digit number where the sum exceeds the next whole ten (such as 28 + 5). The idea is to notice that these sums are similar to single-digit addition facts. Then they do the same without visual models, breaking down the single-digit number into two parts (first part completes the ten). The lesson also contains word problems and pattern exercises.

 Sums that go over to the next ten Let's add 59 + 5 so that we first complete 60. 59 +  5           |    \ 59 + 1 + 4     60   + 4 = 64 The 5 is broken into two parts: 1 and 4. That is because 59 and 1 makes sixty. Then, we have 60 and 4. We get 64. 9 and 1 make a ten. We get 6 tens. 59 + 5 = 64

1. Circle ten little cubes to make a ten. Count the tens and ones. Write the answer. a. 13 + 9 = ______ b. 15 + 8 = ______ c. 17 + 7 = ______ d. 24 + 7 = ______ e. 25 + 6 = ______ f. 37 + 9 = ______ g. 36 + 6 = ______ h. 48 + 4 = ______ i. 58 + 5 = ______

2. Complete. Break the second number into two parts so that you complete the next ten.

 a.   28  +  8                      /      \   28 +   2   + ____    30  + ____ = ______ b.    47  +  5                   /      \  47 +   3   + ____     50  + ____ = ______ c.    79  +  9                       /      \   79 + ____ + ____       80  + ____ = ______ d.   39  +  3                      /      \   39 + ____ + ____  40  + ____ = ______ e.    27  +  5                  /      \  27 + ____ + ____ ______ + ____ = _____ f.    38  +  7                       /      \   38 + ____ + ____ ______ + ____ = _____

3. Write the additions that the number line pictures illustrate. Think how long each line is. a.  ____ + ____ = ________ b.  ____ + ____ = ________

4. Show these additions on the number line by drawing two lines.

 a.   19 + 7 = _____ b.   14 + 18 = _____ 5. Solve the problems. Write a number sentence for each problem, not just the answer.

 a.  Benjamin wants to buy a kite that costs \$30.      He has saved \$22.      How much more money will he need? b.  Natasha had already saved \$20. She earned \$5 by      selling eggs, and earned \$5 more for selling fruit.      How much money does she have now? c.  Mom bought 28 fruit trees and has planted     eight of them. How many still need planted? d.  Thirty-seven people attended Uncle Sam's     50th birthday party. Thirty-two of them came     before noon. How many came after noon? e.  Dad bought a bunch of 40 grapes and ate half of them.     Then, little sister ate seven grapes. How many are left now?

6. Continue the patterns. COMPARE the columns, and NOTICE what is the same.

 a.  8  +  1  = _______     8  +  2  = _______     8  +  3  = _______     8  +  4  = _______     8  + ____ = _______     8 + ____ = _______ b.  28  +  1  = _______     28  +  2  = _______     28  +  3  = _______     28  +  4  = _______     28 + ____ = _______     28 + ____ = _______ c.  78  +  1  = _______     78  +  2  = _______     78  +  3  = _______     78  +  4  = _______     78 + ____ = _______     78 + ____ = _______

This lesson is taken from Maria Miller's book Math Mammoth Add & Subtract 2B, and posted at www.HomeschoolMath.net with permission from the author. Copyright © Maria Miller. The lesson addresses the following Common Core standards for 2nd grade: 2.OA.1, 2.NBT.5, and 2.MD.6.

#### Math Mammoth Add & Subtract 2-B

A self-teaching worktext for 2nd grade that covers mental addition and subtraction with two-digit numbers, and regrouping in addition and subtraction (carrying & borrowing).