Doubles and Halves

45 minutes, 4th grade math – multiplication and division unit

Common Core:

4.NBT.5 Multiply a whole number of up to four digits by a one-digit wholenumber, and multiply two two-digit numbers, using strategies basedon place value and the properties of operations. Illustrate and explainthe calculation by using equations, rectangular arrays, and/or areamodels. 4.OA.5 Generate a number or shape pattern that follows a given rule. Identifyapparent features of the pattern that were not explicit in the rule itself. Learning Objective:

Students are able to generate equations using principles of doubles and halves.

Students can explain how equations using doubles or halves are related.

Lesson:

Today we are going to learn about doubles and halves. Pass out a blank piece of paper to each student

to keep on their desk. Make sure they have a pencil out.

Have students stand in a circle. Count together how many people are in class – write this number on the

board as: # of students x 4= ?.

Give the students a “hot potato” and have them pass it around the circle one time counting by 4’s. After

the potato makes it around the circle one time, ask the students to give me the answer to the equation

on the board.

Next, write # of students x 8= ? Have the students pass the potato around the circle one time and give

me the answer to the equation.

Look at the board, could we have figured out the answer to the second equation without actually

passing the potato around the circle?

Have each student go back to their desk and using the blank piece of paper “predict” what the answer

will be to the first equation if we pass the potato around the circle two times. Write down which

numbers will change and tell how they will change?

Get back into a circle, let’s check your predictions! Count by four and pass the potato around the circle

two times. Did you predict the right answer? What happened to the total? Can we write our new

equation? What numbers changed and how?

Ok, back to your desk and blank paper. This time we are going to count around the circle by 8 and go

around the circle two times. Can you predict what the answer will be to the second equation? Write

down which numbers will change and tell how they will

change?

Test this out with the potato. Did you predict the right

answer? What happened to the total? Can we write our

new equation? What numbers changed and how? How

is this similar to the first prediction?

Desk and paper! What if we pass the potato around the circle two times, but instead of counting by

four, we count by two… what predictions can you make about the number we will end up with? What

will the new equation look like? What numbers that will change?

Test it out. Were your predictions right?

Now I will break the students into two equal groups and have them pass the potato around their circle

one time. Before they do this, I would like them to talk as a small group about what number they will

end up on and how they figured this out?

Go back to your blank page. Think about all of these different equations that we made. How are all of

these equations related?

Collect the blank page to review understanding, but let students know that I will be giving this paper

back for them to keep in their math notebook. This is important information!

Get the students to talk in a group

to answer these questions. Then

debrief by group.

EXIT TICKET

Name: __________________

Today I learned:____________________