Addition Algorithms

Addition Algorithms S. Matthews

Partial-Sums Method for Addition Add from left to right and column by column. The sum of each column is recorded on a separate line. The value of each digit is determined by its place in the numeral.

Let’s practice the value of digits for Partial-Sums. In the problem 23 + 45, we first add the 2 and 4. However, the 2 is worth 2 tens, and the 4 is worth 4 tens. So we say 20, not 2; and 40, not 4.

Let’s practice the value of digits for Partial-Sums. Your turn. What do we say when adding the hundred’s place for 376 + 832?

You’ve got it! We say 300, not 3; and 800, not 8. What is the sum of the 100’s place?

Can’t fool you! In 376 and 832, the 3 is worth 300, and the 8 is worth 800. 300 + 800 is 1,100 or eleven hundred.

Let’s practice the value of digits for Partial-Sums. Let’s continue. What do we say when adding the tens place for 376 + 832?

That’s right! We say 70, not 7; and 30, not 3. What is the sum of the 10’s place?

Can’t fool you! In 376 and 832, the 7 is worth 70, and the 3 is worth 30. 70 + 30 is 100 or ten tens.

Take a look at the steps for addition using the Partial-Sums Method. Then we’ll practice the method some more.

+ 435 398 Add the 100’s: 300 + 400 = 700 Add the 10’s: 90 + 30 = 120 + 13 Add the 1’s: 8 + 5 = 833 Find the total

Now, you try the Partial- sums method using the numbers we practiced.

+ 832 376 1100 Add the 100’s: 300 + 800 = 100 Add the 10’s: 70 + 30 = + 8 Add the 1’s: 6 + 2 = 1,208 Find the total

You are good! Let’s try just one more.

+ 285 479 600 Add the 100’s: 400 + 200 = Add the 10’s: 70 + 80 = 150 + 14 Add the 1’s: 9 + 5 = 764 Find the total

Excellent! I know you’ve got the hang of it. Don’t forget, in the Partial-Sums method for addition, you: • add the 100’s, • add the 10’s, • add the 1’s. • Then add the sums you just found. (the partial sums)

Keep practicing. Peace!

Addition Algorithms