EM2007SRB_G3_OPE.ccc.qxd 1/3/07 9:34 AM Page 57
Operations and Computation
Partial-Sums Addition Method
There are different methods you can use to add. One of these is
called the partial-sums method. It is described below. You may
have a favorite addition method of your own. Even if you do, make
sure that you can also use the partial-sums method.
Here is the partial-sums method for adding
2-digit or 3-digit numbers:
Did You Know
?
Another word for method
is algorithm. A method is
a clear set of rules used
to solve a problem. So is
an algorithm.
1. Add the 100s.
2. Add the 10s.
3. Add the 1s.
4. Add the sums you just found (the partial sums).
Add 248 ! 187 using the partial-sums method.
100s 10s
Add the 100s.
Add the 10s.
2
! 1
200 ! 100 ∑
3
40 ! 80 ∑
1
Add the 1s.
8!7∑
Add the partial sums.
300 ! 120 ! 15 ∑
4
4
8
0
2
1
3
1s
8
7
0
0
5
5
248 ! 187 " 435
Numbers with 4 or more digits are added in the same way.
Use the partial-sums method to add.
1. 34 ! 62
2. 34 ! 88
3. 123 ! 456
4. 408 ! 393
Check your answers on page 337.
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Operations and Computation
You can use base-10 blocks to show how the partial-sums
addition method works.
Use base-10 blocks to add 248 ! 187.
Each base-10 cube is worth 1.
Each base-10 long is worth 10.
And each base-10 flat is worth 100.
Add the blocks in each column. Then find the total.
100s
10s
1s
300
120
15
248
187
!
Find the total. 300 ! 120 ! 15 " 435
248 ! 187 " 435
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