# Lesson: Estimation Techniques: x­ Computations of 3 Digit Numbers

Tara Smith E.l. Haynes Pcs Washington, DC
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### Lesson Objective

SWBAT use estimation techniques to solve whole number computations (multiplication) up to 3 digit numbers

### Lesson Plan

Materials Needed: DN worksheet, dry erase markers, white board, pencils, IND Worksheet.
Vocabulary: rounding, estimation, actual, place value, product, multiply
……….
Do Now (5 min): Teacher gives each student a DN worksheet and asks them to complete the work as quickly and quietly as possible. DN today is a multiplication drill. Students should only be given half of the sheet.

Opening (2 -3 min): Teacher quickly reviews answers to the Do Now and then says, “Yesterday we reviewed estimation techniques when dealing with amounts up to \$1,000. Today, we are going to continue working with our estimation techniques. By the end of this lesson, you will be able to use estimation techniques to solve whole number computations (multiplication) up to 3 digit numbers.

Direct Instruction (10 min): Teacher begins “Ok! Let’s quickly review front end rounding and regrouping! The two steps to front end rounding are on the board.” Teacher should write the following on the board.

1) Add the digits of the two highest place values
2) Insert zeros for the other place values

The teacher continues, “Who would like to read them for me? Who can give me an example of when they used this technique, and in class example will do [Answers will vary]. Great! Now who can tell me what regrouping is? Why is it helpful when looking for an approximate answer? [Answers will vary]. Great job everyone! We can now begin adding and subtraction our 3 digit numbers for today. Let me show you how I want you to work on these problems today. Watch as I do this one on the board. ” Teacher writes the following on the board:

754 x 420 =
Which Strategy?: Rounding
700 x 400 = 280,000

Teacher says, “Ok, now, I know that a lot of you are sitting there thinking, I CAN’T MULTIPLY NUMBERS THAT BIG! Well you are wrong! How can count the number of zeros in my final estimation  Exactly!  Now who can count how many zeros are in the two numbers in my expression?  Exactly! Does anyone see a pattern? [yes, they both have four zeros!] So everyone in this room knows 7 x 4, or can count up to get 7 x 4, so if you know 7 x 4 you can solve this problem because you just have to multiple 7 x 4 and then add 4 zeros! Ok, watch as I complete another one.”

860 x 532 =
Which Strategy?: Rounding
900 x 500 = 450,000

"You will be completing problems almost identical to the ones I completed on the board. The challenge still stands: 10 seconds or less for each problem! I want you to specify which strategy you used to get your estimate or approximate answer. Let’s get started.”

Guided Practice (8-10 min): Teacher says, “Now, I will give you five problems to do together in groups of 2 or 3 on your own paper. Help each other as you work, because in a minute I will have you do some problems on your own. Let’s get started.” Teacher writes the following on the board and gives each student time to solve the problems together in small groups.

1. 738 x 721 =
Which Strategy?: _____________________
Solve:__________________________________

2. 562 x 309 =
Which Strategy?: _____________________
Solve:__________________________________

3. 780 x 651 =
Which Strategy?: _____________________
Solve:__________________________________

4. 621 x 825 =
Which Strategy?: _____________________
Solve:__________________________________

5. 218 x 645 =
Which Strategy?: _____________________
Solve:__________________________________

Independent Practice (10 min): The teacher reviews the answers to the Guided Practice with the class and then passes out the IND practice worksheet.

Closing (2-3 min): Teacher calls the attention of the students back toward the front of the class to quickly review the answers to the Independent Practice/ ask what we learned about.

### Lesson Resources

 IND lesson 9 estimation   Classwork 232 DN multipy multiple digit   Starter / Do Now 253