6 Ways to Teach Rounding in Third Grade, With Answers

Rounding asks which multiple of ten or hundred is nearest to a number. Begin with place value and distance so that a digit rule has meaning. CCSS 3.NBT.A.1 identifies rounding whole numbers to the nearest ten or hundred as a third-grade place-value task. The six examples below are original practice ideas.

1. Name the endpoints

For 47 rounded to the nearest ten, name 40 and 50 before deciding. Forty and fifty are consecutive multiples of ten surrounding 47. Do not compare 47 with arbitrary nearby numbers such as 46 and 48.

2. Draw the distance

Put 40 and 50 on a number line and mark 47. The distance to 40 is 7; the distance to 50 is 3. Since 3 is smaller, 47 rounds to 50. Try 42: it is 2 from 40 and 8 from 50, so 42 rounds to 40.

3. Locate the midpoint

The midpoint between 40 and 50 is 45. Numbers below it are nearer 40; numbers above it are nearer 50. At exactly 45, both distances are 5. Explain that the usual elementary whole-number rounding convention chooses the greater multiple at the midpoint: 45 rounds to 50. Do not tell a child that 45 is actually closer to 50.

4. Change the requested place

For 347 to the nearest hundred, the endpoints are 300 and 400. The distances are 47 and 53, so 347 rounds to 300. To the nearest ten, the endpoints are 340 and 350; the distances are 7 and 3, so 347 rounds to 350. The requested place changes the question.

5. Explain an incorrect answer

Present this invented response: “62 rounds to 70 because every number rounds up.” Ask the learner to draw 60, 62, and 70. Sixty-two is two from 60 and eight from 70, so 62 rounds to 60. Invite the learner to correct the explanation, not merely cross out the answer.

6. Make a number that fits

Ask for a whole number that rounds to 80 to the nearest ten. One answer is 78. Under the convention above, the full set is 75 through 84. Check boundary examples: 74 rounds to 70; 85 rounds to 90.

Independent check and answers

Try 36 to the nearest ten, 83 to the nearest ten, 250 to the nearest hundred, and 649 to the nearest hundred. Answers are 40, 80, 300, and 600. Ask for a number-line explanation for at least one answer.

If the learner cannot identify the endpoints, practice multiples of ten or hundred first. If endpoints are correct but decisions are not, work on comparing distances. Use fewer problems with an explanation rather than more problems that repeat the same misunderstanding.