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Estimate and check: 3rd grade math

Estimate and check reasonableness. A free 3rd grade lesson plan, a question set with answers and a printable sheet with its key. Copy it and make it yours.

Lesson plan

Goal

  • Students can do this: estimate and check reasonableness.

Teach (10 min)

  • An estimate is a quick answer that is close. Round each number to a friendly one, then do the math.
  • 38.7 + 21.2: round to 40 + 21 = 61. The exact answer should be near 61.
  • To check where the point goes in 6.8 × 3.1, think 7 × 3 = 21. So about 20, not 2 or 200.
  • Work one example on the board while students say each step aloud, then do one together.

Practise (15 min)

  • Students work the printable sheet in pairs, then alone.
  • Or practise it as a game with no sign-up: https://peabody.kids/math/base10.estimate?lesson=6-base10-estimate-1&at=3

Exit ticket (5 min)

  • Three questions on a slip:
  • 1. Round each number to the nearest whole number, then subtract to estimate 30.6 − 4.5.
  • 2. Round each number to the nearest whole number, then add to estimate 12.7 + 30.7.
  • 3. Round each number to the nearest whole number, then add to estimate 12.1 + 36.3.

Question set

10 questions that read in words, easiest first. Questions that need a picture are on the printable sheet below.

  1. Round each number to the nearest whole number, then subtract to estimate 30.6 − 4.5.
  2. Round each number to the nearest whole number, then add to estimate 12.7 + 30.7.
  3. Round each number to the nearest whole number, then add to estimate 12.1 + 36.3.
  4. Round each number to the nearest whole number, then add to estimate 27.3 + 21.6.
  5. Round each number to the nearest whole number, then add to estimate 3.81 + 40.9.
  6. Round each number to the nearest whole number, then add to estimate 4.9 + 35.44.
  7. Round each number to the nearest whole number, then subtract to estimate 30.18 − 16.35.
  8. Round each number to the nearest whole number, then add to estimate 34.89 + 11.1.
  9. Round each number to the nearest whole number, then subtract to estimate 60.7 − 55.8.
  10. Round each number to the nearest whole number, then multiply to estimate 6.58 × 4.7.
Answers
  1. 26
  2. 44
  3. 48
  4. 49
  5. 45
  6. 40
  7. 14
  8. 46
  9. 5
  10. 35

Printable sheet

Name: ____________________   Date: ____________

Estimate and check (3rd grade)

  1. Round each number to the nearest whole number, then add to estimate 21.5 + 7.7.
  2. Round each number to the nearest whole number, then add to estimate 14.1 + 14.4.
  3. Round each number to the nearest whole number, then add to estimate 28.7 + 19.4.
  4. Round each number to the nearest whole number, then subtract to estimate 25.74 − 16.93.
  5. Round each number to the nearest whole number, then add to estimate 6.51 + 33.6.
  6. Which is the best estimate of 239.158 ÷ 3.94?
  7. Round each number to the nearest whole number, then subtract to estimate 39.62 − 14.22.
  8. Round each number to the nearest whole number, then multiply to estimate 37.55 × 8.28.
  9. Which is the best estimate of 9.6 × 48.3?
  10. Which is the best estimate of 31.236 ÷ 1.37?
  11. Which is the best estimate of 80.96 ÷ 1.6?
  12. Which is the best estimate of 248.16 ÷ 9.4?
Key
  1. 30
  2. 28
  3. 48
  4. 9
  5. 41
  6. about 60
  7. 26
  8. 304
  9. about 500
  10. about 20
  11. about 50
  12. about 30

Written by Peabody from its own skill pages. Free, no ads, no sign-in. Children can practise this on Peabody. More from teachers: teacher-shared resources.