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Students will be able to round whole numbers to the nearest ten or hundred.
- Lay out a piece of masking tape on the floor, labeled like a number line with numbers 0-30 (write 0, 10, 20, and 30 in red for an easy visual reference).
- Invite students to gather near the number line. Then invite one student to stand on a number (i.e. 17) and instruct them to jump to the nearest ten.
- Point out that the student jumped to a higher number (20).
- Repeat with a few more students and numbers (i.e. 11, 6, 2, 28).
- Explain, "Today we are going to learn how to round whole numbers to the nearest ten or hundred, using number lines to help us."
Explicit Instruction/Teacher modeling(13 minutes)
- Explain that RoundingNumbers is a way of making numbers simpler so that they are easier to think about. The value of the rounded number is close to the original number, but not exact. Rounding numbers helps us perform calculations more easily or think about approximate amounts of things.
- Give students an example (i.e. if you spent 22 minutes riding your bike, you might round the number 22 to the nearest ten and say you’d been riding for about 20 minutes).
- Ask students to think about and share (with an elbow partner) other examples of when it might be helpful to round a number (i.e. amount of money spent at the grocery store, how many chips you ate at a Super Bowl party, how many licks it takes to get to the centre of a tootsie pop).
- On the board, display or draw a number line that goes from zero to 10.
- Circle the number 10, then highlight the distance from five to 10 in one colour and explain that the numbers in the highlighted region are closer to 10 than zero.
- Circle zero, then highlight the distance from zero to five in a different colour, explaining that the numbers in this region are closer to zero than 10.
- Display a new number line or add onto the number line so that it goes up to 30. Then, give a few examples on the number line (22 rounds down to 20, 27 rounds up to 30).
- Point out that five is midway between zero and 10. Explain that when there is a five in the ones place, the number is rounded up. Show students an example on the number line (i.e. 15 rounds up to 20).
- Display or draw a number line with numbers in the hundreds place (i.e. from 100 to 300, counting by tens) and explain, "When rounding numbers to the nearest hundred, the digit in the tens place tells us whether to round up or down."
- Go through several examples (i.e.round 243 to the nearest hundred). Underline the tens place in each example. For each example, ask students to show you a finger pointing up if they think the number should round up, or down if they think it should be rounded down.
Guided practise(10 minutes)
- Hand out the Jump-a-Round worksheet and solve the first problem with the class as an example. Leave the number lines on the board as reference for students.
- Have students complete the rest of the worksheet with a partner as you circulate and check in with students.
Independent working time(15 minutes)
- Hand out the Real World Rounding worksheet and have students complete it independently.
- Circulate and offer support as needed. Go over the worksheet with the class when finished.
- Split the lesson into two parts, focusing only on rounding to the nearest ten in the first lesson before moving on to rounding to the nearest hundred.
- Give students additional practise rounding to tens using coloring pages. See additional resources.
- Have students apply the skills learned in this lesson to solve addition problems. See additional resources.
- Using prepared flashcards, hold up numbers for the class to see. As you hold up each card, have students point up if they think it should be rounded up, or down if they think it should be rounding down. Observe student responses.
- After going through all the flashcards with the class, hand out a flashcard to each student and instruct them to round it to the nearest ten or hundred and write their answer on the card. Collect the cards as an exit ticket.
Review and closing(5 minutes)
- Explain that you are going to give all students a chance to jump and round. Have all students stand in front of their chairs. Tell students that you are going to call out a number and if they would round UP to get to the nearest ten, they should JUMP. If they would round DOWN to the nearest ten, they should SIT down. Call out several numbers.
- Repeat the game, but have students round to the nearest hundred.