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 60 + 4 = 64 The 5 is broken into two parts: 1 and 4. |
9 and 1 make a ten. 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).
Download ($5.65). Also available as a printed copy.