For more practice,
click here to view
the worksheet for
this lesson

The Wonder Number Lessons

Lesson No. 4:  Addition, Double-Digit

Understanding place value in double digit addition can be difficult.  Introducing this concept on the Wonder Number Board makes it easier for students to visually see for themselves that adding sets of numbers is simply counting in a quicker form.

Before beginning double digit addition, it may be beneficial for your students to quickly review the place value and chip trading section in the Comparison Lesson.

The first two numbers to be added are 26 and 43.  Start by placing a green chip on 26.  Remind the student that ones are counted horizontally from left to right across the board.  First add the three ones in 43 by placing yellow chips on 27, 28, and 29.  Remind the student that tens are counted vertically from top to bottom down the board.  Then add the four tens from 43 by placing red chips on 39, 49, 59, and 69 (see fig 24).  The student will discover the answer is 69.  To self-check, lift up the last red chip and verify the answer. 

The next two numbers to be added are 33 and 44.  Start by placing a green chip on 33.  First add the four ones in 44 by placing red chips on 34, 35, 36, and 37.  Then add the four tens from 44 by placing yellow chips on 47, 57, 67, and 77 (see fig 25).  The student will discover the answer is 77.  To self-check, lift up the last yellow chip and verify the answer.