That'll Be a Dollar Ninety-Nine: A Rounding Numbers Lesson Plan
Rounding is an important topic for elementary school students to master - and one that they will use later in life as well. By the time students have reached the fifth grade, they should be able to round numbers to the nearest tens, hundreds, and thousands. You can teach your students the concept and importance of rounding by using this lesson plan.
A good rounding numbers lesson plan begins with direct instruction about what exactly rounding is. Give students the following scenario to introduce the concept of rounding:
"You're at the store, and you find a toy that costs $1.99. When you come home, your mother asks you how much the toy was, and you tell her 'It was about two dollars.' Why did you say that? Why didn't you say 'It was about one dollar?' After all, it cost a dollar, plus another ninety-nine cents, right?"
Let students discuss the answer to this question. They should realize that $1.99 is much closer to two dollars than to one dollar. Explain that when you say that an object costing $1.99 costs two dollars, you are actually rounding. Tell students that rounding is when you find an "easier" number that is the whole number you are thinking of. Tell students that in the above example, you were rounding "to the nearest dollar," and you rounded up to two dollars.
Whole Class Instruction and Practice
Explain to students that when you round, you essentially find a number that has fewer non-zero digits. Start by discussing how to round to the nearest ten. Draw a large number line on the board with the numbers 10, 20, and 30 circled and larger than the rest. Then write a number on the board, such as 18. Ask students which two "big" numbers 18 is between, and they should answer 10 and 20. Then have them identify which of the two "big" numbers 18 is closer to. It would be useful to have a number line available to help the students decide. (They should answer "20.") Discuss with them the fact that they have just rounded up.
Give each student ten small objects as manipulatives, such as beans. Point to the number 18 again, and tell them "Let's see how many numbers we would have to add in order to get to twenty." Then count out two beans and say out loud "Nineteen...twenty - I needed two beans. Now let's see how many numbers we would have to subtract in order to get to ten. (Count aloud) seventeen, sixteen, fifteen, fourteen, thirteen, twelve, eleven, and ten. I needed eight beans to get to ten." Inform students that they should round to the number that needed the fewest beans - in this case, twenty. Let them use the number line together with the beans to help them round several more numbers individually or in small groups. This review activity is particularly helpful for kinesthetic learners and other learners who benefit greatly from manipulatives.
Give students a list of numbers to round to the nearest ten. If students are able to round these numbers successfully, they have mastered the concept. You can also circulate during the individual/group practice and listen to students to see whether they can round successfully. Keep in mind that this rounding numbers lesson plan can be repeated to teach the concept of rounding to the nearest hundred, thousand, and more, but you should make sure to review the concept of place value first.