Beacon Lesson Plan Library
Pac Man Subtraction
Katherine McQuown Polk County Schools
Description
Pac man threedigit subtraction (renaming tens) is taught in a game format using visual symbols, auditory responses (gobbling), and tactile stimuli (touch counting dots).
Objectives
The student explains and demonstrates the addition and subtraction of whole numbers (up to three digits or more) using concrete materials, drawings, symbols, and algorithms.
Materials
Paper
Pencil
Chalk
Chalkboard
Associated File (download attached file to view before lesson)
Preparations
1. Gather materials listed  chalk, pencil, paper.
2. Create and copy assessment test containing five threedigit subtraction problems with three problems requiring renaming of tens. Space problems so students have room for diagrams.
3. Donwload Associated File for teacher use.
Procedures
This lesson only covers 3 digit subtraction with regrouping. It is taught in game format using visual symbols, auditory responses (gobbling), and tactile stimuli (touch counting dots).
1. Ask students if they have ever played Pac man. What does he do? (He eats the ghost.) Say, “Today we are going to play Pac man while practicing subtraction. We will hide and gobble up ghosts. Let me demonstrate with an easy problem.”
2. On the board write 846 minus 325 in vertical format and say, “ Pac people are on top and ghosts are on the bottom of this subtraction problem.” Draw a Pac man around the six and a ghost around the five in the problem. Say, “Pac man has enough power to gobble up six dots. Let’s draw six dots in front of his mouth. The ghost is hiding under the fifth dot. Let’s hide the ghost by drawing him around the fifth dot. Everyone ready, let’s gobble. Gobble, gobble, gobble, gobble, bluhhhhhhlllllll!” Draw a doodle line through the first five dots (or erase them) as the dots and ghost get gobbled up. Then say, “ How many dots are left? (One) Write this answer below the problem. Six ones minus five ones equals one in the one’s place.” (See attachment for diagram)
3. Next, draw Mrs. Pac man around the four in the ten’s place (mouth facing up) and a ghost around the two beneath. Say, “Mrs. Pac man has enough power to gobble up four dots. Let’s draw four dots in front of her mouth. The ghost is hiding under the second dot. Let’s hide the ghost by drawing him around the second dot. Ready, let’s gobble. Gobble, bluhhhhhhlllllll!” Draw a doodle line through the first two dots (or erase them) as the dots and ghost get gobbled up. Then say, “ How many dots are left? (Two) Write this answer below the problem. Four tens minus two tens equals two in the ten’s place.”
4. Next draw a Pac man (mouth facing left) around the eight and a ghost around the three. Say, “Grandpa Pac man has enough power to gobble up eight dots. Let’s draw eight dots in front of his mouth. The ghost is hiding under the third dot. Let’s hide the ghost by drawing him around the third dot. Ready, let’s gobble. Gobble, gobble, bluhhhhhhlllllll!” Draw a doodle line through the first three dots (or erase them) as the dots and ghost get gobbled up. Then say, “ How many dots are left? (Five) Write this answer below the problem. Eight hundreds minus three hundreds equals five in the hundred’s place.”
5. After modeling this easy problem without renaming, model another problem, renaming tens to ones. On the board write 873 minus 148 with digits in vertical format. Draw Mr. Pac man around the three and the three dots after him. Draw the ghost around the eight. Say, “Can we hide the ghost? (No)” Students should see that they could not hide the ghost because there is no eighth dot. Say, “Help Mrs. Pac man, Mr. Pac man needs a power pellet!” Slash the seven in the ten’s column, writing a six above it and place the borrowed ten in front of the three, so thirteen is inside Mr. Pac man. Say, “Seven tens is equal to six tens plus one ten. Now Mr. Pac man has one ten plus three ones or a power of thirteen. Let’s add ten more dots so there are thirteen dots altogether after Mr. Pac man and hide the ghost under number eight.” Draw a doodle line through the first eight dots (or erase) and say, “Gobble, gobble, gobble, gobble, gobble, gobble, gobble, bluhhhhhhlllllll”, as the dots and ghost get gobbled up. Say, “Thirteen ones minus eight ones equals five in the ones place.” (See Associated File for diagram.)
6. Next, draw Mrs. Pac man around the six in the ten’s place and draw six dots. Draw the ghost around the four and hide the ghost under the fourth dot. At the same time say, “Mrs. Pac man has enough power to gobble up six dots. Let’s draw six dots in front of her mouth. Where is the ghost hiding? Let’s hide the ghost by drawing him around the fourth dot. Ready, let’s gobble. Gobble, gobble, gobble, bluhhhhhhlllllll!” Draw a doodle line through the first four dots (or erase them) as the dots and ghost get gobbled up. Then say, “ How many dots are left?” (Two) Write this answer below the problem. Say, “Six tens minus four tens equals two in the ten’s place.” (See Associated File for diagram.)
7. Finally, draw Grandpa Pac man (facing left) around the eight in the hundred’s place and a ghost around the one beneath. Draw the eight dots and a ghost around the first dot. At the same time say, “Grandpa Pac man has enough power to gobble up eight dots. Let’s draw eight dots in front of his mouth. The ghost is hiding under the first dot. Let’s hide the ghost. Ready, let’s gobble. Bluhhhhhhlllllll!” Draw a doodle line through the first dot (or erase it) as the dots and ghost get gobbled up. Then say, “ How many dots are left? (Seven) Write this answer below the problem. Eight hundreds minus one hundred equals seven in the hundred’s place.”
8. Assign one third of the class to stand at the board with chalk and erasers. The other students will have pencils and paper on their desks. Orally give the class a subtraction problem similar to one of the problems you modeled on the board for students to solve on their paper and chalkboard. Ask students, “ How much power does Mr. Pac man have? Can he eat the ghost or does he need help from Mrs. Pac man?” Have students draw dots, rename (if necessary), and hide ghosts. Say, “Ready, let’s gobble.” Students gobble aloud in unison crossing out (or erasing) the dots and ghost, counting the dots left, and writing their answer under the one’s column. Circulating, observe student’s diagrams, answers, and explanations of the process.
9. Have students draw Mrs. Pac man and the ghost in the ten’s column. Ask, “ How much power does Mrs. Pac man have?” Have students draw dots and hide ghosts. Say, “Ready, let’s gobble.” Students gobble aloud in unison crossing out (or erasing) the dots and ghost, counting the dots left, and writing their answer under the ten’s column. Circulating, observe student’s diagrams, answers, and explanations of the process.
10. Have students draw Grandpa Pac man and the ghost in the hundred’s column. Ask, “How much power does Grandpa Pac man have?” Have students draw dots and hide ghosts. Say, “Ready, let’s gobble.” Students gobble aloud in unison crossing out (or erasing) the dots and ghost, counting the dots left, and writing their answer under the hundred’s column. Circulating, observe student’s diagrams, answers, and explanations of the process.
11. Repeat steps 8 through 10, switching students until all students have worked at least two problems at the board.
12. If using a problem with a zero in the ten’s place, have students rename their ten’s using the hundred’s digit with the ten’s digit. For example, in the problem 304 minus 126, slash the 30 tens making it 29 tens and 10 ones. Then add the ten ones to the four ones placing 14 inside Mr. Pac man. (See Associated File.)
13. Test students with a teacher made assessment containing five threedigit subtraction problems. Three problems should require renaming of tens. Four out of the five must be done correctly with Pac man diagrams to achieve a passing score of 80%.
Assessments
Test students with a teacher made assessment containing five threedigit subtraction problems. Three problems should require renaming of tens. Four out of the five should be done correctly with Pac man diagrams.
Web Links
Web supplement for Pac Man Subtraction AAA Third Grade Math
