# Addition of two and three digit whole numbers

Subject:

Math

3

Title – Addition of two and three digit whole numbers
By – Kristy Brooten
Primary Subject – Math
Secondary Subjects –

Concept to be taught:          Addition of two and three digit whole numbers with trading of tens for hundreds and ones for tens

II.          Prerequisite skills:
Basic addition facts; some 2 digit addition; place value for 3 digit numbers and familiarity with its relationship to base ten blocks; be able to write number sentences; vocabulary: addends, sum

III.          Materials:
Base ten blocks, overhead power of ten blocks, blank transparency, overhead markers, worksheets

Mathematics as problem solving.
Mathematics as reasoning.
Mathematics as communication.
Mathematics as connections.
Concepts of whole number operations.
Whole number computation.

V.          Lesson Development:

A.          Motivation
(Pass out base ten blocks and write “Party List” on board –

Miss Hamm: 29

Mr. Horn: 24)

Problem question: We’re going to have a Halloween party for our class and Mr. Horn’s class! Our class is in charge of bringing one brownie for every person that will be there. We need to know how many brownies to make but all we have is how many people are in each individual class! What are we going to do?

Using questioning, guide students toward grouping 10 ones blocks and trading for 1 tens rod, grouping ten tens rods and trading for 1 flat.

Pairs: Can you come up with a total number of brownies we need to make? What’s the easiest way to add it all up? Can you draw me a picture of what you did?

B.          Information Getting
(Discussion/discovery)

Share responses: highlight the grouping and trading idea or suggest it if no one has come up with it. Ask class to try adding by using grouping and trading – go over with overhead blocks – show our class and Mr. Horn’s class à uh-oh! Too many ones! Trade ten ones for a ten. Draw picture of this problem on overhead (circle 10 ones to indicate trade).

I think the other two third grade classes might feel a little left out if we don’t invite them to the party. Let’s add them to our list. There are 28 kids in Mrs. Burres’ class and 31 in Mr. Twain’s class. How many brownies to do need to make total? With your partner, use your blocks to find the answer and then draw a picture to show what you did.

Students will come across new dilemma, too many tens!

What should we do now with all of these tens? Ask for suggestions. If a group says trade ten tens for a flat, highlight that idea and have them draw it on the board. Go over this same problem with the overhead blocks on the overhead just like part one. More than ten ones à uh-oh! Trade. More than ten tens à uh-oh! Trade ten tens for one hundred. Draw picture of same problem on overhead, circling ten ones and ten tens to indicate trade.

Let’s try adding some more problems like this. A new problem: 35 + 42 + 34. Follow same procedure with overhead blocks, waiting for the “uh-oh!” from students and asking them to supply answers. Go over same problem with drawing.

One more problem: 27 + 39 + 18 + 21. Let’s start with drawing this one. Draw tens and ones, again waiting for the “uh-oh!” and asking students to supply answers.

C.          Closure/Conclusion

Guided practice:
Let’s get back to our Halloween party. The second graders are having a party too – since you are such an intelligent class, they asked for your help! There are 20 kids in Miss Ryrie’s class, 26 in Mr. O’Hara’s class, 27 in Mrs. LaHaye’s class and 35 in Mrs. Bell’s class. How many brownies do they need to make? Solve in pairs, have two sets of pairs compute on board, discuss. If need more guided practice, be ready with numbers for 1st grade classes.

Independent practice:
In pairs, work on worksheet: use base ten blocks (if needed – if don’t need manipulatives, just draw) to group and trade in order to add and then draw picture

Review:
Share pair work, going over problem on overhead

Summarizing by questioning: What do we do when we’re adding 2 digit numbers and we have too many ones? Too many tens?

D.          Evaluation
Pairs: Worksheet – The fourth grade classes were feeling a little left out, so they decided to have a party with brownies too. How many brownies do they need? (Give party list) Draw picture, use blocks if you need to.

When finished, see if you came up with the same thing another group did.

VI.          Integration

To life: real life problem