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Estimating Square Roots and Division Worksheet

Mental maths lesson 27: Estimate divisions and square roots · Set 309 · 40 questions
TalentJR

How to do it in your head (Guess, divide, average): Division: round the divisor to the nearest ten and find the closest multiple of it. Square root: guess the nearest whole root, then divide the number by your guess. Average the guess and the answer of the division, and round to 1 decimal place.

NameDateTime takenScore ___ / 40
  1. 1.√94 to 1 decimal place? (a) 9.8 (b) 9.9 (c) 10.0 (d) 9.7
  2. 2.Best estimate of 781 ÷ 38? (a) 20 (b) 2000 (c) 200
  3. 3.√89 to 1 decimal place? (a) 9.4 (b) 9.3 (c) 9.1 (d) 9.2
  4. 4.√28 to 1 decimal place? (a) 5.5 (b) 5.6 (c) 5.3 (d) 5.4
  5. 5.Best estimate of 1619 ÷ 22? (a) 810 (b) 81 (c) 8100
  6. 6.Best estimate of 1414 ÷ 68? (a) 20 (b) 2000 (c) 200
  7. 7.√85 to 1 decimal place? (a) 9.1 (b) 9.3 (c) 9.2 (d) 9.4
  8. 8.Best estimate of 3481 ÷ 52? (a) 7000 (b) 70 (c) 700
  9. 9.Best estimate of 3023 ÷ 34? (a) 101 (b) 10100 (c) 1010
  10. 10.Best estimate of 8224 ÷ 86? (a) 9100 (b) 91 (c) 910
  11. 11.Best estimate of 3855 ÷ 52? (a) 7700 (b) 77 (c) 770
  12. 12.Best estimate of 5730 ÷ 69? (a) 8200 (b) 820 (c) 82
  13. 13.√26 to 1 decimal place? (a) 5.0 (b) 5.1 (c) 4.9 (d) 4.8
  14. 14.√92 to 1 decimal place? (a) 9.7 (b) 9.8 (c) 9.9 (d) 9.6
  15. 15.√21 to 1 decimal place? (a) 4.5 (b) 4.7 (c) 4.8 (d) 4.6
  16. 16.√32 to 1 decimal place? (a) 6.0 (b) 5.9 (c) 5.8 (d) 5.7
  17. 17.Best estimate of 800 ÷ 56? (a) 13 (b) 130 (c) 1300
  18. 18.√56 to 1 decimal place? (a) 7.4 (b) 7.5 (c) 7.7 (d) 7.6
  19. 19.Best estimate of 4341 ÷ 69? (a) 620 (b) 6200 (c) 62
  20. 20.√48 to 1 decimal place? (a) 6.8 (b) 6.6 (c) 6.9 (d) 6.7
  21. 21.√98 to 1 decimal place? (a) 10.1 (b) 9.9 (c) 10.0 (d) 9.8
  22. 22.√76 to 1 decimal place? (a) 8.8 (b) 8.7 (c) 9.0 (d) 8.9
  23. 23.√20 to 1 decimal place? (a) 4.8 (b) 4.7 (c) 4.5 (d) 4.6
  24. 24.Best estimate of 1504 ÷ 47? (a) 30 (b) 300 (c) 3000
  25. 25.√35 to 1 decimal place? (a) 6.0 (b) 6.2 (c) 5.9 (d) 6.1
  26. 26.Best estimate of 3263 ÷ 56? (a) 5400 (b) 540 (c) 54
  27. 27.Best estimate of 1650 ÷ 36? (a) 41 (b) 4100 (c) 410
  28. 28.√96 to 1 decimal place? (a) 9.6 (b) 9.8 (c) 9.5 (d) 9.7
  29. 29.Best estimate of 3417 ÷ 74? (a) 49 (b) 4900 (c) 490
  30. 30.Best estimate of 1752 ÷ 36? (a) 4400 (b) 440 (c) 44
  31. 31.Best estimate of 2895 ÷ 41? (a) 7200 (b) 72 (c) 720
  32. 32.Best estimate of 1544 ÷ 32? (a) 510 (b) 51 (c) 5100
  33. 33.√84 to 1 decimal place? (a) 9.0 (b) 9.1 (c) 9.2 (d) 8.9
  34. 34.√61 to 1 decimal place? (a) 7.9 (b) 7.8 (c) 8.0 (d) 8.1
  35. 35.√66 to 1 decimal place? (a) 8.2 (b) 8.1 (c) 8.0 (d) 7.9
  36. 36.Best estimate of 1845 ÷ 76? (a) 230 (b) 2300 (c) 23
  37. 37.√86 to 1 decimal place? (a) 9.5 (b) 9.3 (c) 9.4 (d) 9.2
  38. 38.√74 to 1 decimal place? (a) 8.5 (b) 8.8 (c) 8.7 (d) 8.6
  39. 39.√79 to 1 decimal place? (a) 9.2 (b) 9.1 (c) 8.9 (d) 9.0
  40. 40.Best estimate of 479 ÷ 34? (a) 16 (b) 1600 (c) 160

Answer key

  1. 9.7
  2. 20
  3. 9.4
  4. 5.3
  5. 81
  6. 20
  7. 9.2
  8. 70
  9. 101
  10. 91
  11. 77
  12. 82
  13. 5.1
  14. 9.6
  15. 4.6
  16. 5.7
  17. 13
  18. 7.5
  19. 62
  20. 6.9
  21. 9.9
  22. 8.7
  23. 4.5
  24. 30
  25. 5.9
  26. 54
  27. 41
  28. 9.8
  29. 49
  30. 44
  31. 72
  32. 51
  33. 9.2
  34. 7.8
  35. 8.1
  36. 23
  37. 9.3
  38. 8.6
  39. 8.9
  40. 16

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