Partial Sums

Presented by

Robin Seldin

• When students begin to learn how to add two-digit numbers they are usually taught “carrying”.

• A different way to do this is called the “Partial Sums” algorithm.

• Partial sums focuses on place value when solving two-digit addition problems.

• It teaches children to start on the left and add the tens first.

• Moving from left to right (just like in reading!) actually makes sense to the children and they have a better understanding of why and how they get their answer.

• Here is an example of the Partial Sums Algorithm:

4 5

+ 3 8

7 0 Step 1: Add the tens (40 + 30 = 70) and write the

sum. + 1 3 Step 2: Add the ones (8 + 5 = 13) and write the

sum.

8 3 Step 3: Add the tens and ones (70 + 13 = 83) to get the final answer.

• Here is another example of the

Partial Sums Algorithm:

6 7

+4 5

100 Step 1: Add the tens (60 + 40 = 100) and write the

sum. +1 2 Step 2: Add the ones (7 + 5 = 12) and write the sum.

112 Step 3: Add the tens and ones (100 + 12 = 112) to get the final answer.

• http://www.youtube.com/watch?v=4UexBOa7u8Y