Lesson
2-7A
Common
Core
3.NBT.2 Fluently add and
subtract within 1000 using
strategies and algorithms
based on place value,
properties of operations,
and/or the relationship
between addition and
subtraction.
Adding with an
Expanded Algorithm
place-value blocks
How can you break large addition
problems into smaller ones?
Find the sum 243 1 179.
Each digit in each number can be modeled
with place-value blocks. You can use place
value to add the numbers.
MATHEMATICAL
Guided Practice
PRACTICES
Do you know HOW?
Do you UNDERSTAND?
In 1 and 2, name the value of the digits
in these numbers.
5. Reason How are the three
problems in the example related
to the 3-digit problem you started
with?
1. the 7 in 700
2. the 4 in 542
3. Complete these steps to find
375 1 412.
Hundreds Tens
Ones Total
300
70
5
1 400
1 10
12
6. Communicate Suppose you were
adding 405 1 527. What would the
tens problem be? Why?
7. Write the problems you could use
to find 623 1 281.
4. Find 308 1 494.
Independent Practice
In 8 and 9, complete the steps to find each sum.
8. 550 1 423
Hundreds
Tens
500
50
1 400
1 20
Ones
0
13
Total
9. 546 1 232
Hundreds
Tens
500
40
1 200
1 30
In 10–15, find each sum.
10. 185 1 613.
11. 730 1 168.
12. 645 1 314.
13. 315 1 251.
14. 288 1 103.
15. 561 1 332.
eTools
6
Ones
6
12
Total
Step 1
Step 2
Break 243 1 179 into smaller problems.
Think about the place values of each
number.
Hundreds
Tens
Ones
200
40
3
+ 100
+ 70
+ 9
300
110
12
Then add the sums of all the places.
300
110
+ 12
422
MATHEMATICAL
Problem Solving
PRACTICES
16. John read a book with 377 pages.
Jess read a book with 210 pages.
How many pages in all did they
read?
17. Persevere Anne made a necklace
with 176 beads. Lynn made one
with 254 beads. How many beads
did they use in all?
18. There are 431 people watching a
soccer game at a stadium. Then,
245 more people arrive. How many
people are at the soccer game now?
19. Reason Bill needs to find 318 1 230.
Into what three smaller problems
can he break this addition?
20. Writing to Explain Paulo wants
to add the points his favorite
basketball team scored in the last
two games. The team scored
137 points and 112 points. Describe
how Paulo can add these numbers
using smaller problems.
21. Communicate Leah wants to
find the sum 335 1 420. She wants
to break the problem into easier
problems. Does she need to find a
sum for the ones? Explain.
22. Persevere A movie theater sold
275 tickets on Monday and
226 tickets on Tuesday. How many
tickets did the movie theater sell in
all?
23. Which of the following shows the
sum of the hundreds, tens, and
ones for 331 1 516?
A 800 1 40 1 6
B 800 1 40 1 7
C 700 1 40 1 8
D 400 1 80 1 8
Lesson 2-7A
7