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Estimating Square Roots and Division Worksheet

Mental maths lesson 27: Estimate divisions and square roots · Set 339 · 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.√20 to 1 decimal place? (a) 4.7 (b) 4.6 (c) 4.8 (d) 4.5
  2. 2.√92 to 1 decimal place? (a) 9.5 (b) 9.6 (c) 9.7 (d) 9.4
  3. 3.Best estimate of 1809 ÷ 49? (a) 36 (b) 3600 (c) 360
  4. 4.√45 to 1 decimal place? (a) 6.5 (b) 6.8 (c) 6.7 (d) 6.6
  5. 5.Best estimate of 6968 ÷ 76? (a) 8700 (b) 870 (c) 87
  6. 6.Best estimate of 3295 ÷ 52? (a) 6600 (b) 660 (c) 66
  7. 7.Best estimate of 5167 ÷ 66? (a) 74 (b) 740 (c) 7400
  8. 8.√56 to 1 decimal place? (a) 7.7 (b) 7.5 (c) 7.4 (d) 7.6
  9. 9.√32 to 1 decimal place? (a) 5.8 (b) 5.9 (c) 6.0 (d) 5.7
  10. 10.√96 to 1 decimal place? (a) 9.9 (b) 9.7 (c) 9.8 (d) 9.6
  11. 11.Best estimate of 4288 ÷ 83? (a) 540 (b) 54 (c) 5400
  12. 12.√58 to 1 decimal place? (a) 7.6 (b) 7.7 (c) 7.5 (d) 7.8
  13. 13.√26 to 1 decimal place? (a) 5.1 (b) 5.2 (c) 5.0 (d) 5.3
  14. 14.Best estimate of 2292 ÷ 46? (a) 460 (b) 4600 (c) 46
  15. 15.Best estimate of 1851 ÷ 48? (a) 370 (b) 37 (c) 3700
  16. 16.Best estimate of 1264 ÷ 89? (a) 1400 (b) 140 (c) 14
  17. 17.√89 to 1 decimal place? (a) 9.4 (b) 9.5 (c) 9.2 (d) 9.3
  18. 18.Best estimate of 2613 ÷ 89? (a) 29 (b) 2900 (c) 290
  19. 19.Best estimate of 4822 ÷ 73? (a) 690 (b) 6900 (c) 69
  20. 20.Best estimate of 833 ÷ 23? (a) 4200 (b) 42 (c) 420
  21. 21.Best estimate of 2523 ÷ 31? (a) 840 (b) 84 (c) 8400
  22. 22.Best estimate of 2162 ÷ 79? (a) 2700 (b) 27 (c) 270
  23. 23.√87 to 1 decimal place? (a) 9.3 (b) 9.2 (c) 9.1 (d) 9.0
  24. 24.√44 to 1 decimal place? (a) 6.6 (b) 6.9 (c) 6.8 (d) 6.7
  25. 25.Best estimate of 6777 ÷ 76? (a) 850 (b) 8500 (c) 85
  26. 26.√98 to 1 decimal place? (a) 9.9 (b) 9.7 (c) 9.8 (d) 10.0
  27. 27.√28 to 1 decimal place? (a) 5.6 (b) 5.5 (c) 5.3 (d) 5.4
  28. 28.√66 to 1 decimal place? (a) 8.2 (b) 7.9 (c) 8.1 (d) 8.0
  29. 29.Best estimate of 1245 ÷ 41? (a) 3100 (b) 310 (c) 31
  30. 30.√71 to 1 decimal place? (a) 8.5 (b) 8.7 (c) 8.6 (d) 8.4
  31. 31.Best estimate of 849 ÷ 56? (a) 140 (b) 1400 (c) 14
  32. 32.Best estimate of 2363 ÷ 79? (a) 30 (b) 300 (c) 3000
  33. 33.√61 to 1 decimal place? (a) 7.6 (b) 7.7 (c) 7.5 (d) 7.8
  34. 34.Best estimate of 5069 ÷ 57? (a) 840 (b) 8400 (c) 84
  35. 35.Best estimate of 6571 ÷ 76? (a) 8200 (b) 820 (c) 82
  36. 36.Best estimate of 2153 ÷ 26? (a) 720 (b) 7200 (c) 72
  37. 37.Best estimate of 1088 ÷ 26? (a) 36 (b) 360 (c) 3600
  38. 38.√65 to 1 decimal place? (a) 8.1 (b) 7.9 (c) 7.8 (d) 8.0
  39. 39.Best estimate of 2986 ÷ 86? (a) 33 (b) 3300 (c) 330
  40. 40.Best estimate of 849 ÷ 52? (a) 170 (b) 1700 (c) 17

Answer key

  1. 4.5
  2. 9.6
  3. 36
  4. 6.7
  5. 87
  6. 66
  7. 74
  8. 7.5
  9. 5.7
  10. 9.8
  11. 54
  12. 7.6
  13. 5.1
  14. 46
  15. 37
  16. 14
  17. 9.4
  18. 29
  19. 69
  20. 42
  21. 84
  22. 27
  23. 9.3
  24. 6.6
  25. 85
  26. 9.9
  27. 5.3
  28. 8.1
  29. 31
  30. 8.4
  31. 14
  32. 30
  33. 7.8
  34. 84
  35. 82
  36. 72
  37. 36
  38. 8.1
  39. 33
  40. 17

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